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THIS  BOOK  IS  DUE  ON  THE  DATE 
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POSTED  AT  THE  CIRCULATION 
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DEC  0  3 1998 


■'^' 


GREENHOUSES 

THEIR  CONSTRUCTION  and  EQUIPMENT 


W.  jrWRIGHT, 

Director,  New   York  State  School  of  Agriculture 
at    Alfred    University.      Formerly    Assist- 
ant Professor  of  Horticulture  at  the 
Pennsylvania  State  College 


ILLUSTRATED 


NEW    YORK 

ORANGE  JUDD  PUBLISHING  COMPANY,  INC. 

LONDON 
KEGAN  PAUL.  TRENC^,  TRIBNER  &  CO.,  Limited 

1923 


Copyright,    1917,   by 
ORANGE  JUDD  COMPANY 

All  Rights  Reserved 

Entered  at  Stationers'  Hall 
London,   England 


Printed   in   U.  S.  A. 


^^^iuimGoUmgm 


TO    MY    FATHER 

IN   WHOSE    FLUE-HEATED,    SHED   ROOF    PROPAGATING 

HOUSE    I    FIRST    LEARNED   TO    LOVE    THE 

SMELL    OF   THE    SOIL 


1048S 


PREFACE 

In  1912  the  author  was  asked  to  present  a 
paper  before  the  National  Vegetable  Grow- 
ers' Association  on  the  construction  and 
equipment  of  greenhouses,  with  special  refer- 
ence to  the  vegetable  forcing  industry.  Much 
of  the  data  given  in  this  paper  had  been 
hitherto  unavailable  and  was  based  on  an 
extensive  personal  survey  of  greenhouse 
owners  and  operators,  supplemented  by  per- 
sonal experience  and  observation.  So  great 
has  been  the  demand  for  this  data  that  at  the 
request  of  the  Orange  Judd  Company,-  the 
author  has  undertaken  to  incorporate  it  in 
book  form.  The  present  volume  attempts 
a  more  thorough  discussion  of  the  subject 
than  could  be  given  in  a  single  paper.  It 
is  based  upon  a  series  of  lectures  given  be- 
fore the  author's  classes. 

This  is  the  second  book,  dealing  exclu- 
sively with  this  subject,  which  has  been  pub- 
lished in  the  United  States.  The  former, 
written  by  Prof.  L.  R.  Taft  and  published  by 


vi  PREFACE 

the  Orange  Judd  Company  in  1893,  has  been 
the  standard  and  only  work  devoted  entirely 
to  greenhouse  construction  as  adapted  to 
American  conditions.  To  this  and  to  Pro- 
fessor Taft  the  author  of  the  present  volume 
is  deeply  indebted.  It  is  not  intended  that 
this  second  book  shall  supersede  the  former 
but  that  it  shall  supplement  it  and  emphasize 
present-day  features.  Probably  in  no  line  of 
horticulture  has  so  great  progress  been  made 
in  the  past  quarter  of  a  century  as  in  floricul- 
ture and  vegetable  forcing.  The  develop- 
ment of  the  forcing  house  has  been  no  less 
rapid. 

No  attempt  has  been  made  to  discuss  the 
question  of  greenhouse  construction  from  the 
standpoint  of  the  manufacturer,  although 
due  credit  must  be  given  to  the  energy  and 
ingenuity  which  he  has  displayed  in  meeting 
the  rapidly  changing  conditions  and  in  the 
excellence  of  present-day  construction.  It 
is  probably  not  too  much  to  say,  that  the 
development  of  the  flower  and  vegetable 
forcing  industry  has  been  largely  dependent 
upon  the  improvement  which  has  been  made 
in  the  manufacture  of  greenhouse  material 
and  equipment. 

The  real  purpose  of  the  book  is  to  pre- 


PREFACE  vli 

sent  to  the  reader  such  information  con- 
cerning the  location,  adaptation,  general  con- 
struction and  equipment  of  greenhouses  as 
will  enable  him  to  decide  upon  the  type  of 
house  best  adapted  to  his  special  needs;  to 
supervise  or  assist  if  need  be  in  its  construc- 
tion or  erection;  to  arrive  at  some  conclu- 
sion as  to  the  equipment  most  likely  to  ren- 
der the  service  required,  and  the  probable 
cost.  A  special  effort  has  been  made  to  make 
the  volume  of  service  to  the  present  owner 
of  a  greenhouse  and  to  those  who  may  con- 
template building,  whether  it  be  a  small 
private  house  or  a  large  commercial  range. 
The  arrangement  of  topics  is  made  with 
reference  to  a  pedagogical  system  which 
it  is.  hoped  will  be  of  service  to  the  teacher 
and  student. 

It  is  practicall}^  impossible  to  give  in- 
dividual credit  for  all  the  sources  drawn  up- 
on in  the  preparation  -of  this  volume.  Spec- 
ial mention  should  be  made,  however,  of  the 
assistance  given  by  the  manufacturers  of 
greenhouse  building  material  and  for  the 
many  excellent  illustrations  which  they  have 
furnished.  When  practicable,  the  source  of 
these  illustrations  is  given.  Free  use  has 
also  been  made  of  bulletins  of  the  various 


viii  PREFACE 

Experiment    Stations    and    of    the    United 
States  Department  of  Agriculture. 

The  book  is  offered  with  a  full  conscious- 
ness of  its  shortcomings,  but  with  the  hope 
that  it  may  be  of  some  definite  service  and 
that  it  may  serve  as  a  focusing  point  for 
criticisms  and  suggestions,  out  of  which 
may  be  born  a  fuller  knowledge  through  the 
experience  and  observation  of  its  readers. 

W.  J.  Wright. 
New  York  State 
School  of  Agriculture,  1917, 
Alfred,  New  York. 


CONTENTS 

CHAPTER*  I 
A  General  Survey 1_9 

Classes  of  sash-beds — Classes  of  green- 
houses— Evolution  of  the  greenhouse. 

CHAPTER  n 

Sash-bed  Coxstructiox         ....      10-34: 

Hotbeds,  location  of,  sash,  pit,  manure  for — 
Coldframes — Cold  or  storage  pits — Forcing 
boxes — Gable  roof  sash-beds — ^la.ts  and 
shutters — Care  of  sash-bed  materials. 

CHAPTER  HI 
Greenhouse  Proper — General  Con- 
siderations             35-49 

Location — Arrangement — Size  of  houses — 
Pitch  of  roof — Measuring  the  pitch — Length 
of  rafters, 

CHAPTER  IV 
Greenhouse  Architecture     .        .        .  50-62 

Lean-to  or  shed-roof  houses — Even-span  or 
span-roof  houses — Uneven  span  houses — 
Ridge-and-furrow^  houses — ^Side  hill  houses 
— Curved  roof  houses — Curved  eave  houses 
— Circular  houses. 

CHAPTER  V 
Structural  Material 63-79 

Glazing  sill — Eave  plate — Gutter — Glazing 
bars — Side  posts — Sash  bars — Gable  bars — 
Drip  gutters — Purlins — Ridge — Kinds  of 
wood  used — Framing. 

ix 


X  CONTENTS 

CHAPTER  VI 
Framework,  Methods  of  Erecting  .        .       80-96 

Cardinal  virtues  of  a  good  greenhouse  frame- 
work— Foundations  and  walls — Wood-frame 
houses — Semi-iron  frame  houses — All-metal 
frame  houses. 

CFIAPTER  VII 

Glazing  and  Painting 97-120 

Greenhouse  glazing  an  art — Glass  to  use — 
Size  of  glass — Lapped  glazing — Butted  glaz- 
ing— Putty — Setting  the  glass — How  to  esti- 
mate putty — Glazing  points — Precautions — 
Liquid  putty — Substitutes  for  glass — Kind  of 
paint — Amount  of  paint  required — Shading 
— Glazing  ladder. 

CHAPTER  VIII 

Ventilation  and  Ventilating 

Machinery 121-141 

Systems  of  greenhouse  ventilation — Side 
ventilation — Overhead  ventilation — Size  of 
ventilators — Hanging  ventilator  sash — Venti- 
lator operating  machinery — Shafting — Shaft 
hangers — Gearing — Ventilator  arms — Capa- 
city of  ventilating  apparatus — Sliding  shaft 
system. 

CHAPTER  IX 
Beds,  Benches  and  Walks  ....   142-157 

Advantages  and  disadvantages  of  benches — 
.Raised  beds — Wood  benches — Iron  frame 
benches — Concrete  benches — Height  and 
width  of  benches — Arrangement  of  benches 
and  walks — Walks  and  curbs. 

CHAPTER  X 

Greenhouse  Heating 158-166 

The  principles  of  greenhouse  heating — Heat- 
ing with  flues — Hot  water  vs.  steam  heating 
— Combination  heating  systems — Heating 
coils — Cast  iron-  and  wrought  iron  pipes  for 
heating. 

CHAPTER  XI 

Hot  Water  Installation  ....  167-187 
General  principles — Formula  for  determin- 
ing velocity  of  water  in  heating  systems — 
Estimating  radiation — Amount  of  pipe  re- 
quired— Size  of  flow  pipe — Length  of  coils 
— Expansion  tank — Pressure  systems. 


CONTEXTS  xi 

CHAPTER  XII 
Steam  Installation 188-109 

General  principles — Size  and  length  of  coils 
— Size  of  supply  and  return  pipes — Valves — 
High  pressure  steam  heating — Vacuum  and 
vapor  systems — Arrangement  of  boilers — 
Steam  pumps  and  steam  traps. 

CHAPTER  XIII 

Boilers,  Fuels  and  Flues  ....   200-225 

Essentials  of  a  boiler — Grate  surface — Fire 
surface — Types  of  boilers — Cast  and  wrought 
iron  boilers — Styles  of  cast  iron  boilers — 
Styles  of  wrought  iron  boilers — Steam  and 
hot-water  boilers — Boilers  for  burning  hard 
and  soft  coal — Under-fed  boilers — Self-stok- 
ing boilers — Size  of  chimneys  and  flues — 
Arrangement  of  flues. 

CHAPTER  XIV 

Water  Supply  and  Irrigation  .        .        .   226-241 

Amount  of  water  required — Types  of  pumps 
— Capacity  of  pumps — Powder  required — 
Hydraulic  rams — Capacity  of  rams — Wind- 
mills for  pumping — Storage  tanks — Capacity 
of  storage  tanks — Overhead  irrigation — 
Sub-irrigation. 

CHAPTER  XV 
Concrete  Construction        ....   242-256 

How  concrete  is  made — Kind  of  sand  re- 
quired— Kind  of  stone  or  gravel  required — 
Crushed  stone — How  materials  are  propor- 
tioned— Directions  for  mixing — Amount  of 
w^ater  required — Estimating  materials  — 
Forms  for  walls — Reinforcing — Walks  and 
floors — Water-proofing — Concrete  blocks — 
Cost  of  concrete  work. 

CHAPTER  XVI 
Plans  and  Estimates 257-262 

Basis  of  estimate — Average  costs — Detailed 
estimates — Information  required  in  obtain- 
ing estimates. 


LIST  OF  ILLUSTRATIONS 

pac;e 
Conservatories,  New>  York  Botanical  Gardens 

Frontispiece 

1  Hotbed  in   operation      ......      10 

2  Standard  hotbed  sash    ......     12 

3  Double-glass    sash 15 

4  Plan"    for    permanent    hotbed        .  .  .  .19 

5  Permanent  hotbed  of  concrete  with  cast-iron  sills     19 

6  Plan  for  temporary  hotbed   .  .  .  .  .20 

7  Type    of    hotlDed    used   when    a    large    amount    of 

heat  is  required  .....  .20 

8  Usual  type  of  concrete  hotbed     .  .  .  .21 

9  Hotbed   arranged   for  heating  bj^  flues  .  .     23 

10  A  good  type  of  coldframe   .  .  .  .  .24 

11  Coldframe  with  sash  removed       .  .  .  .25 

12  A  cold  or  storage-pit    .  .  .  .  .  .26 

13  Sash-bed   attached    to   basement  of   dwelling       .     28 

14  Types  of  forcing  boxes  or  plant  forcers      .  .     29 

15  Forcing  boxes  in  use  on  a  commercial  scale       .     29 

16  Gable-roof   sash-bed  heated  by  manure        .  .     30 

17  Rye  straw  mats  rolled  for  storage       .  .  .31 

18  Hotbed  covered  with  mat  and  shutter   .        .  .32 

19  Private  range  of  C.  E.  Chapman,  Oakdale,  N.  J.  .     37 

20  Ground  plan  of  range  shown  in  Fig.   19       .  .38 

21  Commercial  range  of  Hoerber  Bros.,  DesPlaines, 

111 .  .39 

22  Ground  plan  of  range  shown  in  Fig.  21       .  .40 

23  Part  of  vegetable  forcing  range  of  Searls  Bros., 

Toledo,  Ohio 41 

24  Diagram  showing  method  of  measuring  pitch  of 

roof ^        ...     42 

25  Commercial    range    of    C.    H.    Metcalfe,    ^Milford, 

Mass 43 

26  Diagram    showing   how  heat   and   light    rays    are 

lost  by   reflection      ......     44 

26a  Diagram  showing  pitch  of  roof  necessary  to  pre- 
sent an  angle  of  90  degrees  to  the  sun's  rays 
in  winter     .        .  ...  •  .45 

27  An   uneven    span    greenhouse        .  .  .  .53 

28  Uneven   span,   side-hill   vegetable   house        .  .     55 

xili 


xiv  LIST  OF  ILLUSTRATIONS 

PAGE 

29  Ridge-and-furrow  houses  wrecked  by  a  storm     .     57 

30  Diagram  showing  that  the  same  amount  of  roof 

is  reciuired  for  several  small,  connected  houses 

as  for  one  large  house  covering  the  same  area     58 

31  Diagram  of  side-hill  range   .... 

32  Curved-eave  and  circular  types  of  construction 

33  Two    methods     of     framing    a     semi-iron     frame 

greenhouse        ...... 

34  Types    of   sills        ...... 

35  Tj^pes  of   eave   plates    .  ..... 

36  Types  of   gutters  ..... 

37  Type  of  gutter  for  curved-eave  houses 

38  Cross    section    of   corner    bar 

39  Types  of  wood  sash  bars      .... 

40  Two  types  of  patented  metal   sash  bars 

41  King  "Channel  Bars"    ..... 

42  ''U-Bar"  type   of  sash  bar   .... 

43  Gable    rafter  ...... 

44  Combination  eave  plate  and  gutter      . 

45  Pipe  strap  for  fastening  sash  bars  to  purlins 

46  ''Pecky"    C3^press  .  .  .  . 

47  The    concentric    system   of   construction 

48  A  type  of  all-metal   flat  rafter   construction 

49  Plan   for   an   all-wood   frame    greenhouse    . 

50  Two    methods     of    framing    a    semi-iron     frame 

house         ....... 

51  Structural  steel  post  with  board  wall  . 

52  Section    of    truss-frame    greenhouse     . 

53  Section    of    combination    truss-frame    greenhouse 

54  ^lethod    of   erecting   a    large    combination    truss- 

frame  greenhouse     ..... 

55  Side  view  of  house  shown  in  Fig.  54   . 

56  A   method     of     erecting     small    all-metal     frame 

houses        ....... 

57  Lapped  glazing     ...... 

58  Putty  knife    . 

59  Machine   for    distributing   putty    . 

60  A,  window  glazing;  B,  greenhouse  glazing  . 

61  Putty  bulb     . 

62  Types    of    glazing   points       .  .  .  • 

63  Glazing  with   double  pointed   glazing  points 

64  Glazing  with    single   glazing   points 

65  Glazing  ladder  used    in    glazing  and   painting 

66  Greenhouse  showing  A.  side  ventilators;  B,  over- 

head or  roof  ventilators   .... 

67  Method   of  under-bench   ventilation 

68  Two  methods  of  hanging  ventilator  sash    . 


LIST  OF  ILLUSTRATIONS  xv 

PAGE 

69  Malleable  iron  shaft  coupling       ....   12Q 

70  Shaft  hangers         .          .          .  .    '     .          .          .130 

71  Open    column   ventilator   gearing  .  .  .131 

72  Open   column   chain   operated  ventilator  gearing  131 
12>  Closed   column   ventilator   gearing        .          .          ,    132 

74  Chain  system  of  operating  ventilators  .  ,    133 

75  Rack-and-pinion  system  of  operating  ventilators  ,133 
16     Ventilators  operated  by  means  of  rods  with  uni- 
versal joints      .  .  .  .  .  .  .135 

11  Device  for  operating  side  ventilators   .  .  .    136 

78  Compact  machine  for  operating  side  ventilators  137 

79  Types    of   ventilator   arms    .....    138 

80  Sliding  shaft  system  for  operating  ventilators    .    141 

81  Cucumbers  growing  in  ground,  no  benches  used.  143 

82  Tomatoes  growing  in  solid  raised  beds       .  .    145 

83  Solid  raised  beds  of  hollow  building  tile    .  .    145 

84  Two   types   of  wood  benches        ....    147 

85  A   type   of  iron   frame   bench        ....    148 

86  Greenhouse    bench    of    concrete    ....    150 

87  Method  of  arranging  benches  in  an  uneven  span 

house         .  .  .         .  .         .         .         .153 

88  An  arrangement  of  benches  in  a  30  foot  house   .    154 

89  Another   arrangement    of   benches    in   a   30  foot 

house        ........    155 

90  A  combination    steam    and    hot    water    heating 

system       ........    162 

91  Under  bench  heating  with  large  cast  iron  pipes  .    165 

92  Diagram  showing  "down  hill"  and  "up  hill"  sys- 

tems of  hot  water  piping       .  ....  170 

93  A  type  of  automatic  air  valve      ....  171 

94  A  method  of  piping  a  medium  size  house   .  .  178 

95  Diagram    showing    under-bench    method    of    hot 

water  piping     .  .  .  .  .  .  .179 

96  Gasoline  engine  arranged  to  circulate  hot  water 

in  a  greenhouse  heating  system       .  .  .    180 

97  Automatic  expansion  tank   ......  182 

98  A  type  of  mercury  "generator"  ....   185 

99  A  corner  coil 191 

100  A   mortise    coil 192 

101  Reducing  valve 195 

102  A  type  of  steam  return  trap         ....    199 

103  A  type  of  "vertical"  or  "square"  sectional  boiler  204 

104  End   view   of  "square"   sectional  boiler   showing 

fire   travel        * 205 

105  Side   view   of   "square"    sectional   boiler    showing 

tire  travel 206 

106  Battery  of  five  cast  iron  sectional  boilers    .  .   207 


xvi-  LIST  OF  ILLUSTRATIONS 

PAGE 

107  A    tj-pe     of    "round"     or     'iiorizoQtal"     sectional 

boiler 208 

108  Corrugated  fire  box  boiler 209 

109  Type  of  tubular  boiler  much  used  in  greenhouse 

heating 210 

110  Battery  of  two  marine  type  boilers  used  in  green- 

house   heating  .  .  .  .  .  .211 

111  Wrought  iron  boiler  without  flues        .  .  ,   212 

112  Sectional  view  of  boiler  shown  in  Fig.  Ill   .  .   213 

113  Altitude  guage 215 

114  Water  column  and  guage     .....  216 

115  Steam  guage         .......  217 

116  Diagram  of  automatic  damper  regulator     .  .   217 

117  Asbestos    pipe    covering         .....   218 

118  Boiler  equipped  for  using  natural  gas  .  .   219 

119  Chimneys  should  extend  above  the  roofs  of  ad- 

jacent  buildings        .  .  . '       .  .  .   224 

120  Pumping  jack        .......   227 

121  Diagram     showing     installation     of     auto-pneu- 

matic  pump      .......  228 

122  A  simple  type  of  hydraulic  ram  ....  232 

123  Plan   for   installing  a  hydraulic  ram    .  .  .  233 

124  Overhead'  irrigation       ......  239 

125  A  type  of  nozzle  used  in  overhead  irrigation       .  240 

126  Greenhouse  bench   arranged  for  sub-irrigation    .  241 

127  Proportions  of  cement,  sand  and  stone  required 

to  form  concrete      ......  245 

128  Form  for  a  concrete  wall    .....  250 

129  Method  of  facing  a  concrete  wall       .         .  .  251 

130  Structure  of  a  concrete   walk      .  *       .         .  .   253 

131  A  small  power  machine  for  mixing  concrete       .  255 


GREENHOUSES 

CHAPTER  I 
A  GENERAL  SURVEY 

It  is  not  the  purpose  of  this  book  to  furnish 
detailed  information  concerning  the  manu- 
facture of  greenhouse  building  material,  for 
the  cutting  and  shaping  of  the  materials  is 
the  work  of  the  mill  and  the  factory.  Its 
purpose  is  rather  to  present  such  informa- 
tion concerning  the  location,  adaptation, 
erection  and  equipment  of  greenhouses  as 
will  enable  the  reader  to  decide  upon  the  type 
of  house  best  adapted  to  his  special  needs;  to 
supervise  or  assist  if  need  be,  in  its  construc- 
tion or  erection;  and  to  arrive  at  some  con- 
clusion as  to  the  equipment  most  likely  to 
render  the  service  required. 

Greenhouses  are  the  result  of  an  attempt 
on  the  part  of  man  to  create  conditions  favor- 
able to  the  growth  of  plants  in  climates  or 
during  seasons  naturally  unfavorable.  They 
must,  therefore,  protect  the  plants  from  cold 
and  storms,  allow  for  an  abundance  of  direct 
sunlight,  provide  for  ventilation  and  in  most 

1 


2  GREENHOUSES 

cases  they  must  be  equipped  with  faciHties 
for  artificial  heating. 

In  a  general  sense,  the  term  greenhouse  re- 
fers to  those  glass  structures  used  for  the 
growing  of  plants.  They  are  for  the  most 
part  above  ground  and  are  house-like  in  ap- 
pearance. There  is,  liowever,  another  gener- 
al class  of  glass  structures  also  used  for  the 
growing  of  plants  but  which  are  low  and 
often  almost  wholly  under  ground.  Unfor- 
tunately, there  is  no  general  term  commonly 
applied  to  them  as  a  class,  but  since  it  is 
common  to  use  in  their  construction  certain 
standard-size  glass  sash,  the  author  ventures 
to  suggest  the  term  sash-bed  as  a  general 
one  to  include  structures  of  this  class;  and  it 
is  so  used  in  this  book. 

CLASSES      OF     SASH-BEDS* 

Hotbeds. — These  are  low  structures,  being 
almost  wholly  under  ground,  but  having  a 
glass  roof  made  up  of  sash  which  are  of  con- 
venient size  to  be  lifted  off,  so  that  the  grow- 
er may  care  for  the  plants.  They  are  usually 
warmed  by  the  heat  generated  by  decaying 
vegetable  matter,  commonly  horse  manure. 

*For  details   see   Chapter  II. 


A  GENERAL  SURVEY  3 

Their  chief  use  is  for  starting  plants  in  early 
spring. 

Coldframes. — These  are  similar  to  hotbeds 
but  are  seldom  heated  and  may  therefore  be 
of  more  shallow  construction,  as  no  pit  is 
needed  to  store  the  manure.  Their  chief  use 
is  for  the  growing  and  protection  of  young- 
plants  after  they  have  been  started  in  hot- 
beds or  forcing  houses,  or  for  the  growing 
of  plants  in  late  spring  after  danger  of  severe 
w^eather  has  passed. 

Coldpits. — These  are  deep  pits  chiefly  used 
for  the  storing  of  bulbs  and  semi-hardy 
plants  during  the  winter.  They  are  usually 
provided  w^ith  sash  roofs  the  same  as  hot- 
beds and  coldframes,  so  that  light  may  be  ad- 
mitted when  desired. 

CLASSES  OF  GREENHOUSES 
Forcing  Houses. — These  are  greenhouses 
used  for  growing  or  "forcing"  plants  at  other 
times  than  at  their  natural  seasons.  Prac- 
tically all  houses  used  by  commercial  florists 
and  vegetable  growers  are  forcing  houses. 
Conservatories. — In  this  class  of  green- 
houses, plants  are  kept  mostly  for  display. 
Often  it  is  not  desired  that  the  plants  so  kept 


-i  GREENHOUSES 

shall  grow  rapidly,  but  that  they  shall  merely 
live.  Often  also  they  house  for  the  most 
part  such  semi-hardy  evergreen  and  other 
ornamental  plants  as  may  be  grown  outside 
during  the  summer.  Such  houses  are  com- 
mon in  parks  and  private  estates.  They  are 
usually  ornamental  in  character,  often  with 
curved  roofs,  and  present  a  lively  contrast  to 
the  severe  simplicity  of  the  commercial  forc- 
ing houses. 

Propagating  Houses. — These  houses  are 
devoted  principally  to  the  propagation  or 
starting  of  plants,  especially  those  grown 
from  cuttings.  As  cuttings  require  little 
direct  sunlight,  these  houses  are  often  erected 
on  the  shady  (north)  side  of  other  green- 
houses or  in  out-of-the-way  places.  They 
should  be  equipped  with  benches,  underneath 
which  the  heating  pipes  should  be  placed  to 
furnish  ''bottom  heat." 

The  term  hothouse,  as  commonly  used,  is 
a  general  term  synonymous  with  greenhouse, 
and  may  be  applied  to  any  of  the  above 
classes. 

The  term  stove  house  is  an  old  one,  origin- 
ally applied  to  any  greenhouse  used  for  tropi- 


A    GENERAL   SURVEY  5 

cal  plants  and  thus  of  necessity  kept  at  a  high 
temperature.  The  use  of  this  term  is  more 
common  in  England  than  in  this  country. 

A  RANGE  of  greenhouses  implies  several 
houses  more  or  less  closely  connected  and 
under  one  management.  The  individual 
houses  may  be  of  any  one  of  the  classes  men- 
tioned above  or  a  combination  of  two  or  more 
classes.     Such  houses  are  often  spoken  of  as 

a  RANGE  OF   GLASS. 

A  range  of  forcing  houses  is  sometimes 
spoken  of  as  a  battery,  and  a  range  of  sash- 
beds  as  a  NEST. 

EVOLUTION  OF  THE  GREENHOUSE 
It  is  said  that  the  Romans,  even  before  the 
time  of  Christ,  possessed  some  knowledge  of 
the  forcing  of  fruits  and  vegetables,  and  util- 
ized for  this  purpose  pits  covered  with  slabs 
of  a  transparent  mineral.  Heat  was  supplied 
by  fermenting  manure,  and  occasionally  by 
furnaces  of  masonry  in  which  a  slow  fire  of 
wood  or  dried  manure  was  kept  burning. 
How  successful  they  were  we  do  not  know; 
but  it  seems  certain  that  if  any  degree  of 
perfection  was  obtained,  it  was  because  of 
the  skill  of  the  gardener  rather  than  because 
of  any  special  merit  of  the  forcing  pits. 


6  GREENHOUSES 

Forcing  houses  seem  to  have  had  their 
origin  in  an  attempt  to  grow  in  the  northern 
countries  of  Europe  fruits  such  as  the  orange 
and  grape,  which  were  grown  to  such  perfec- 
tion in  the  countries  to  the  south.  Thus  in 
England  the  grape  vine  is  hardy,  but  the 
summers  are  too  cool  and  the  seasons  too 
short  to  ripen  the  fruit  to  perfection.  This 
led  to  the  training  of  the  vines  on  the  south 
side  of  buildings  and  walls  that  they  might 
receive  more  fully  the  light  and  heat  of  the 
sun.  Later  there  was  conceived  the  possibil- 
ity of  still  further  protecting  them  by  the  use 
of  glass  sash  leaned  against  the  wall.  From 
this  it  was  an  easy  step  to  the  building  of 
a  rather  permanent  framework  close  to  the 
walls,  on  which  glass  sash  were  placed  when 
required,  forming  a  closed  house.  Sometimes 
the  walls  were  made  hollow  and  slow  fires 
built  within  them  to  give  additional  heat. 
Finally  the  idea  of  heating  the  air  instead  of 
the  walls  on  which  the  vines  were  trained 
resulted  in  the  building  of  brick  and  stone 
stoves  or  fireplaces  within  the  glass  enclos- 
ures. These  houses  were  never  intended  for 
winter  use,  but  simply  to  make  the  summer 
and  fall  conditions  similar  to  those  farther 
south. 


A  GENERAL  SURVEY  7 

The  attempt  to  grow  the  orange  in  these 
northern  cHmates  presented  a  different  prob- 
lem because  the  trees  had  to  be  protected 
during  the  winter.  This  resulted  in  the  build- 
ing of  framework  structures  which  were 
covered  during  the  winter  with  wooden-shut- 
ters and  heated  by  means  of  a  stone  fireplace. 
There  was  little  or  no  glass  used,  but  the 
shutters  were  removed  during  the  summer, 
leaving  nothing  but  the  framework  to  ob- 
struct the  light  and  heat  of  the  sun.  A  house 
of  this  description,  built  early  in  the  17th 
century  by  one  Solomon  de  Gaus  at  Heidel- 
berg, Germany,  is  said  to  have  been  32  feet 
wide  and  some  400  feet  long,  and  to  have 
sheltered  400  orange  trees. 

The  next  decisive  step  in  the  evolution  of 
the  modern  greenhouse  seems  to  have  been  a 
combination  of  the  two  preceding  types,  de- 
signed for,  the  growing  of  plants  during  the 
winter.  They  were  permanent  buildings 
having  opaque  roofs  and  high  side  walls, 
resembling  dwelling  houses,  except  that  they 
were  well  supplied  with  side  windows. 

At  this  time  it  was  thought  necessary  to 
have  opaque  roofs  to  prevent  freezing,  and  it 
became  common  to  have  a  second  story, 
which  was  used  as  a  dwelling  by  the  garden- 


8  GREENHOUSES 

er,  in  order  to  prevent  the  heat  from  escapmg 
or  the  frost  from  ''entering"  through  the 
roof.  It  was  not  until  the  early  part  of  the 
1 8th  century  that  glass  roofs  were  found  to 
l3e  practicable,  and  they  were  even  then  slow 
in  coming  into  use. 

The  first  greenhouses  in  this  country  sug- 
gestive of  the  modern  forcing  house  came  in- 
to existence  toward  the  close  of  the  i8th  cen- 
tury. For  the  most  part  they  were  narrow 
houses  of  the  shed-roof  type,  having  a  solid 
wall  to  the  north  and  a  glass  roof  sloping  to 
the  south.  They  were  warmed  by  flues, 
usually  of  brick,  passing  through  the  entire 
length  of  the  house,  and  connected  with  a 
brick  fireplace  at  one  end  and  a  chimney  at 
the  other.  Following  this,  there  came  in 
rapid  succession,  improvements  in  form  and 
methods  of  construction  and  especially  in 
heating,  both  steam  and  hot  water,  being 
used  early  in  the  19th  century. 

The  real  progress  in  greenhouse  construc- 
tion in  this  country  came  with  the  industrial 
development  of  the  country  after  the  Civil 
War.  The  United  States  census  reports  show 
that  there  was  but  one  commercial  green- 
house prior  to  1800;  only  three  prior  to  1820, 


A  GENERAL  SURVEY  9 

and  only  178  in  i860.  It  was  not  until  1890 
that  greenhouses  had  assumed  sufficient  im- 
portance to  secure  a  place  in  the  census  re- 
ports. At  that  time  there  were  4,659  estab- 
lishments covering  38,823,247  square  feet, 
valued  at  $38,355,722. 

The  following  table  shows  the  total  num- 
ber of  square  feet  under  glass  in  the  United 
States  and  ten  principal  states,  as  shown  in 
the  census  reports  for  1910,  1900  and  1890. 
The  rank  of  the  states  has  changed  material- 
ly during  the  past  30  years. 

AREA   UNDER    GLuVSS    IX    THE    UNITED    STATES    AND    TEN 
PRINCIPAL    STATES.     FROM    CENSUS    REPORTS 

1910  1900  1890 

Tot.  Glass      Gieenh'ses     Tot.  Glass   Greenh'ses*  Tot.  Glass 


sq.  ft 

sq.  ft. 

sq.  ft. 

sq.  ft. 

sq.  ft. 

U.S. 

114,665,276 

105,165,730 

96,230,420 

80,544,862 

38,823,276 

111. 

15,950,853 

14,380,857 

8,744,020 

7,318,744 

3,236,750 

N.    Y. 

15,066,587 

13,878,875 

13,635,440 

11,412,863 

6,947,289 

Penn. 

13,846,672 

12,887,672' 

11,819,610 

9,893,013 

6,066,144 

N.    J. 

8.840,511 

7,984,752 

11,190,250 

9,356,283 

3,703,554 

Ohio 

7,583,562 

7,091,976 

7,970,190 

6,471,049 

2,785,192 

Mass. 

7,382,009 

6,817,585 

8,710,280 

7,290,504 

2,717,946 

Cal. 

5,087,132 

4,422,423 

1,572',480 

1.316,165 

Mich. 

4,122,099 

3,922,772 

2,593,230 

2,170,233 

1,293,443 

Mo. 

2,812,221 

2,545,138 

3,126,400 

2,616,786 

1.240,093 

Iowa 

2,183,182 

1,870,840 

1,436,260 

1,202,149 

Ky. 

1,163,241 

Conn. 

1,060,920 

•Estimated. 


CHAPTER  II 
SASH-BED   CONSTRUCTION 

HOTBEDS 

As  Stated  in  the  preceding  chapter,  hot- 
beds are  low  structures  almost  wholly  under- 


Fig.  1. — Hotbed  in  operation 

ground,  but  having  a  glass  roof  made  up  of 
sash.  They  are  usually  heated  by  ferment- 
ing horse  manure  placed  in  the  bottom,  but 
may  be  heated  by  brick  or  tile  flues,  or  by 
steam  or  hot  water.  Their  chief  commercial 
use  in  for  the  starting  of  early  vegetable  and 
flowering  plants.  In  the  home  garden  they 
may  be  used  for  growing  to  maturity  in  early 
spring  or  late  atitumn,  such  semi-hardy  and 

10 


SASH-BED  CONSTRUCTIOX  ]1 

quick  maturing  vegetables  as  radishes  and 
lettuce,  and  thus  extend  the  season  for  sev- 
eral weeks  or  even  months.  They  may  also 
be  used  for  starting  and  protecting  early  in 
the  season,  other  slower  growing  crops  such 
as  melons,  which  are  not  transplanted  but  are 
allowed  to  mature  in  the  beds.  A  gain  of 
several  weeks  may  thus  be  secured  in  the 
time  of  ripening.  Well  constructed  and  pro- 
tected hotbeds  will  withstand  a  temperature 
as  low  as  zero  if  it  is  of  short  duration. 

Location.^The  location  for  the  hotbed 
should  be  (i)  relatively  high;  (2)  well  drain- 
ed; (3)  exposed  to  the  sun  throughout  the 
day;  (4)  protected  from  north  and  north- 
west winds;  and  (5)  either  comparatively 
level,  or  sloping  toward  the  south  or  south- 
west. For  convenience  it  should  be  near 
some  building  which  may  be  used  as  a  work- 
room, and  should  be  close  to  a  supply  of 
water.  The  south  side  of  a  building  is  often 
an  ideal  location,  although  there  is  some  dan- 
ger, if  the  building  be  a  light  colored  one, 
that  the  hotbed  may  become  overheated. 

Sash. — Standard  hotbed  sash  are  3x6 
feet,  and  from  1%  to  1%  inches  thick,  the 
latter   being   more    durable    but    heavier    to 


12 


GREENHOUSES 


handle.  Since  they  are  subjected  to  especial- 
ly rough  usage,  they  must  be  well  construct- 
ed of  good  material,  and  must  be  kept  well 
painted.  Well  constructed  sash  may  be  se- 
cured from  any  reliable  dealer  in  greenhouse 


Fig.  2. — Standard  Hotbed  Sash 

A,  three  run  sash;   B,  four  run  sash;   C;  Horned  sash; 

X,   iron   rod   to   keep   sash   from   spreading 

material.  They  may  be  of  either  cypress 
or  cedar  and  have  mortise  and  tenon  joints, 
though  the  tenons  should  not  extend  quite 
through  the  bars,  or  they  will  be  more  likely 
to  absorb  moisture  and  thus  decay  rapidly. 
All  joints  should  be  painted  with  thick  lead 
paint  and  should  be  put  together  while  the 
paint  is  green.  Sash  with  a  light  iron  rod  or 
bar  across  the  middle,  connecting  the  side 


SASH-BED  CONSTRUCTIOX  13 

bars,  will  usually  prove  to  be  more  durable, 
as  the  rod  prevents  the  sides  from  spreading. 

Most  hotbed  sash  consist  of  three  rows  of 
glass  so  laid  that  the  water  will  flow  length- 
wise of  the  sash.  For  this  purpose  i8  panes 
of  10  X  1 2-inch  glass  are  reqtiired.  Sash  hav- 
ing four  rows  of  glass  are  not  uncommon, 
but  the  extra  bar  and  laps  obstruct  so  much 
light  that  they  are  less  satisfactory,  and  they 
are  rapidly  going  out  of  use.  They  require 
28  panes  of  8  x  lo-inch  glass.  Sash  may  be 
purchased  either  glazed  or  tmglazed.  When 
time  is  plentiful  and  the  workman  is  handy 
with  tools,  they  may  be  glazed  at  home  at  a 
considerable  saving  in  cost. 

Well  made  sash  may  be  had,  unglazed  and 
unpainted,  at  from  $1  to  $1.25  each.  The 
same  sash  glazed  and  painted  cost  from  $3  to 
$3.50  at  the  factory.  The  price  of  glass  varies 
greatly  from  year  to  year,  but  on  the  average 
will  cost  from  75  cents  to  $1  per  sash. 
Roughly  speaking,  the  sash,  putty  and  paint 
will  cost  about  $2.25,  leaving  from  75  cents 
to  $1.25  for  the  labor  of  glazing  and  painting. 
Sash  of  varying  sizes  are  sometimes  seen,  but 
their  use  is  not  advised.  It  is  seldom  possible 
to  replace  them  as  cheaply  as  when  standard 
size  sash  are  used. 


14  GREENHOUSES 

When  sash  are  glazed  at  home  they  should 
first  be  primed  with  a  coat  of  lead  paint.    On 
looking  them  over  it  will  be  observed  that 
one  of  the  end  bars  is  not  so  thick  as  the 
other,  the  upper  surface  being  in  line  with 
the  bottoms  of  the  grooves  or  channels  made 
to  receive  the  glass.    This  is  the  lower  end  of 
the  sash  and  should  always  be  placed  tow^ard 
the  south.     The  glazing  also  begins  at  this 
end.   In  glazing,  the  first  pane  is  laid  flat,  the 
bottom  of  the  second  lapped  over  the  top  of 
the  first  and  so  on,  small  brads  or  glazing 
points  being  placed  at  the  lower  end  of  each 
pane  and  along  the  sides  to  hold  them  in 
place.     Since  the  lap  obstructs  the  light  it 
should  be  as  narrow  as  possible,  an  eighth 
of  an  inch  being  as  wide  as  necessary.      In 
order  to  obviate  the  necessity  of  cutting  the 
last  glass  to  keep  the  laps  even,  it  is  well  to 
lay  all  the  panes  for  one  row  on  loosely,  and 
to  space  them  before  fastening  any.      They 
should  then  be  puttied  the  same  as  ordinary 
windows,  and  thoroughly  painted. 

A  more  satisfactory  way  of  setting  the 
glass  is  to  bed  them  in  putty  as  described  in 
Chapter  VII,  btit  this  method  is  rarely  used 
with  hotbed  sash.  Sometimes  the  glass  are 
butted;  that  is,  they  are  laid  flat,  end  to  end, 


SASH-BED  CONSTRUCTION 


15 


instead  of  lapped.  This  is  rarely  satisfactory 
for  hotbed  sash;  because  (i)  the  panes  are 
often  not  squarely  cut  and  do  not  fit  well,  and 
(2)  the  sash  have  so  little  pitch  or  slant  when 
in  use  that  water  is  apt  to  run  through  be- 
tween the  panes. 

Some  makers  offer  a  form  of  sash  known 
as  ''horned  sash/'  in  which  the  side  bars  ex- 
tend two  or  three  inches  beyond  the  end  bars. 
These  extensions  make  convenient  handles 
for  carrying,  and  it  is  claimed  that  a  better 
joint  can  be  made  than  when  they  are  cut  off 
flush  with  the  end  bars. 

Double-glass  Sash,  as  the  name  implies, 
are  constructed  with  two  layers  of  glass  with 
an  air  space  of  about  a  half-inch  between. 
They  have  certain  advantages  over  single- 
glass  sash  which  may  be  stated  as  follows: 
(i)  They  give  greater  protection;  (2)  they 
reduce  labor,  as  it  is  not  necessary  to  use 


Fig.  3. — Double   Glass   Sash 


16  GREENHOUSES 

mats  as  late  in  the  season;  (3)  in  moderate 
climates  no  mats  or  supplementary  protec- 
tion is  needed;  (4)  the  plants  receive  sun- 
light during  the  entire  day  when  mats  are 
not  used,  whereas,  with  single  glass  sash, 
the  mats  have  to  be  left  on  until  the  sun 
is  well  up  and  then  have  to  be  replaced  be- 
fore sundown. 

On  the  other  hand,  they  have  several  dis- 
advantages: (i)  The  first  cost  is  often  as 
much  as  50  per  cent,  greater;  (2)  they  are 
heavier  to  handle;  (3)  they  reduce  the 
amount  of  light,  especially  if  the  glass  be- 
comes loosened  so  that  dust  accumulates 
between  the  layers ;  and  (4)  some  users  com- 
plain that  they  are  short-lived  because  moist- 
ure collects  between  the  layers  and  promotes 
rapid  decay. 

The  most  enthusiastic  supporters  of  these 
sash  are  those  who  live  in  climates  where 
this  type  of  sash  never  need  supplementary 
protection,  but  where  it  is  not  safe  to  leave 
single-light  sash  unprotected.  It  is  but  fair 
to  state,  however,  that  their  use  is  rapidly  in- 
creasing, even  in  the  north. 

Temporary  Sash,  made  of  oiled  paper  or 
treated  cloth,  are  sometimes  used  for  special 


SASH-BED  CONSTRUCTIOX  IT 

purposes  and  give  more  or  less  satisfactory 
results.  Directions  for  making  will  be  found 
in  Chapter  VII. 

The  Pit. — As  most  hotbeds  are  heated  by 
fermenting  manure,  a  necessary  part  is  a  pit 
of  some  depth  in  which  it  may  be  placed. 
This  pit  may  be  lined  with  boards,  plank, 
brick,  stone  or  concrete,  the  latter  being  the 
most  satisfactory.  Cypress,  cedar,  chestnut 
and  black  locust  are  the  most  durable,  moder- 
ate price  woods  for  this  purpose.  For  data 
on  concrete  construction  see  Chapter  XV. 

The  depth  of  the  pit  is  determined  by:  (i) 
The  severity  of  the  climate  and  (2)  the  kind 
of  plants  to  be  grown.  As  more  heat  is  pro- 
duced for  a  longer  time  from  a  deep  pit  of 
manure  than  from  a  shallow  one,  it  is  evident 
that  in  cold  climates  and  for  plants  requir- 
ing considerable  heat,  such  as  tomatoes  and 
peppers,  the  pit  must  be  deeper  than  in 
warmer  climates,  or  for  plants  like  cabbage 
or  cauliflower  which  mav  be  s^rown  at  lower 
temperatures.  For  starting  early  vegetable 
plants  in  late  February  or  early  IMarch  in 
the  north,  24  inches  of  manure  will  be  re- 
quired, whereas  in  milder  climates,  or  later 
in  the  season,  12  to  18  inches  will  be  suffi- 


LS  GREENHOUSES 

cient.  The  manure  will  continue  to  give  off 
heat  for  three  to  six  weeks. 

The  dimensions  are  determined  by  the 
sash.  Since  sash  are  6  feet  long  and  are  con- 
structed to  slope  lengthwise  rather  than 
crosswise,  the  width  of  the  pit  north  and 
south  should  be  a  trifle  less  than  6  feet  over 
all.  The  length  is  determined  by  the  num- 
ber of  sash  desired.  Since  they  are  3  feet 
wide,  it  should  be  some  multiple  of  three. 
For  example :  A  two-sash  bed  would  be  6  x  6 
feet,  a  three-sash  bed  6x9  feet,  etc.  It  is 
essential  that  the  pit  be  well  drained  either 
naturally  or  artificially.  If  it  is  to  be  used  in 
early  spring,  it  is  made  the  previous  fall, 
filled  with  straw  or  manure  and  covered  with 
boards  to  keep  out  rain  and  snow.  When 
the  bed  is  to  be  made  this  material  is  re- 
moved, leaving  an  unfrozen  pit  in  which 
the  new  manure  will  heat  more  evenly  and 
be  more  efficient. 

The  upper  or  north  side  of  a  permanent 
hotbed  is  preferably  6  or  8  inches  higher 
than  the  south  side  to  give  the  proper 
slant  to  the  sash.  The  north  side  may  be 
about  15  inches  and  the  south  side  about  9 
inches  above  the  surface  of  the  soil.  The 
sides   are   connected   with   crossbars   placed 


SASII-BED  CONSTRUCTION 


19 


Fig.  4. — Plan   for  permanent  hotbed 

even  with  the  top,  3  feet  apart,  to  serve  as 
rests  for  the  sash  and  to  keep  the  frames 
from  spreading.  The  sides  and  ends  of  the 
frame  are  well  banked  with  fresh  manure  to 
conserve    the    heat.       If   the    plants    are    to 


Fig.  5. — Permanent  hotbed  of  concrete  with  cast-iron  sills 

1)e  grown  in  flats  instead  of  directly  in  the 
soil,  2  inches  of  soil  over  the  manure  will  be 
sufficient.  If  the  plants  are  to  be  grown  in 
the  soil  it  should  be  4  or  5  inches  deep. 


20 


GREENHOUSES 


Temporary  hotbeds  are  sometimes  made 
by  piling  the  manure  on  the  surface  of  the 
ground  and  placing  a  shallow  frame  on  top. 


Ground  Level 

Fig.    6. — Plan    for    temporary    hotbed. 

This  form  is  wasteful  of  manure,  and  the 
settling  of  the  pile  is  likely  to  warp  the  frame 
so  that  the  sash  will  not  fit  tightly.  It  is 
most  often  used  when  a  hotbed  is  needed  and 
a  pit  has  not  been  dug  the  previous  fall. 

Another  method  is  to  dig  a  pit  somewhat 
larger  than  the  frame.  This  is  filled  with 
manure  to  a  little  above  the  ground  level. 


Fig.  7, — Type  of  hotbed  used  when  a  large  amount  of  heat 
is  required  for  a  long  time 


SASH-BED  CONSTRUCTION  21 

On  top  of  this  is  placed  a  frame.  The  ad- 
vantage of  this  form  of  bed  is  that  the  frame 
settles  with  the  manure,  thus  keeping  the 
plants  always  the  same  distance  from  the 
glass.  They  are  also  warmer  on  account 
of  the  greater  quantity  of  manure  used. 

Manure  for  Heating. — Horse  manure  is  al- 
most universally  used  in  hotbeds,  the  pro- 


Fig.  8. — Usual   type   of   concrete    hotbed 

portion  being  about  two  parts  solid  excre- 
ment to  one  part  straw  or  leaves.  Manure 
which  contains  shavings  is  not  satisfactory. 
Preparation  is  made  lO  or  12  days  before  the 
beds  are  wanted.  The  manure  must  be  fresh- 
ly made  and  if  not  moist  is  dampened,  prefer- 
ably with  warm,  though  not  hot  water. 
More  than  enough  manure .  to  £11  .the  pit  is 
proyi(3edj  foritwiH  Shrink,  somewhat  in  vpl- 


22  GREENHOUSES 

lime,  and  some  will  be  needed  to  bank  the 
sides  and  ends.     It  is  placed  in  layers  in  a 
pile  4  or  5  feet  wide,  about  4  feet  high  and 
as  long  as  necessary  to  contain  the  required 
amount,  each  layer  being  lightly  tramped  as 
placed.    This  is  done  under  cover  if  possible. 
After  two  or  three  days,  or  as  soon  as  the 
pile  begins  to  steam,  it  is  re-piled,  the  outside 
of  the  first  pile  being  placed  into  the  center 
of   the    second   to    encourage    even   heating 
throughout.     The  manure  is  moistened  with 
warm  water  if  it  has  become  dry.     If  prop- 
erly made  a  vigorous  fermentation  will  have 
set  in  after  two  or  three  days  and  it  is  then 
ready    to    be    placed    in    the    bed.      If    not 
thoroughly  warmed  through  in  three  or  four 
days  after  the  second  handling,  it  is  re-piled 
again  every  few  days  until  fermentation  is 
established.     Poor  heating  qualities  may  be 
the  result  of:   (i)   Manure  from  poorly-fed 
horses;  (2)  cold  weather;  (3)  too  wet  or  too 
dry  manure;  (4)  too  much  litter  in  the  man- 
ure and  (5)  shavings  or  swamp  hay  used  as 
litter  instead  of  straw  or  leaves. 

If  a  steady  heat  for  several  weeks  is  re- 
quired, the  manure  is  placed  in  the  pit  in  thin 
layers  and  trampled  quite  solidly,  especially 


SASH-BED  CONSTRUCTION 


2'3 


along  the  sides  and  in  the  corners,  keeping  it 
as  level  as  possible.  Unless  the  hotbed  is 
made  so  that  the  frame  settles  with  the 
manure  it  must  be  filled  to  within  2  or  3 
inches  of  the  top  of  the  south  side  of  the 
frame  to  provide  for  settling.  If  it  is  proper- 
ly made,  the  temperature  will  soon  rise  to 
120  degrees  or  more,  but  will  gradually  fall, 
and  when  it  reaches  90  degrees  the  seeds 
may  safely  be  sown.  The  temperature  may 
be  determined  by  plunging  a  reliable  ther- 
mometer through  the  soil  into  the  manure. 
When  a  hotbed  is  arranged  to  be  heated 
by  flues,  drain  or  sewer  tile  is  used,  and  the 
flues  are  connected  with  a  fireplace  at  one  end 


Fig.  9. — Hotbed  arranged  for  heating  by  flues 

of  the  bed  and  a  chimney  at  the  other,  so 
that  the  smoke  and  heat  from  the  fire  travel 
the  whole  length  of  the  bed.     Hot  water  or 


24: 


GREENHOUSES 


steam  pipes  may  be  run  through  these  flues 
if  desired,  or  they  may  be  placed  along  the 
sides  of  the  frame  above  the  soil. 
COLDFRAMES 
The  forcing  house,  because  of  its  conveni- 
ence, possibility  of  heat  regulation  and  com- 
parative cheapness  of  operation  is  rapidly 
taking  the  place  of  the  hotbed  in  a  commer- 
cial way  in  the  starting  of  early  plants,  but 
it  is  promoting  the  use  of  coldframes.  These 
structures  rarelv  receive  artificial  heat  and 


Fig.  10. — A  good  type  of  coldframe  with  angle  iron 
corners,  A. 

are  used  largely  for  the  purpose  of  growing 
and  protecting  plants  during  mid  or  late 
spring,  after  they  have  been  started  in  the 
hotbed  or  forcing  house  and  until  they  are 
ready  to  plant  in  the  open.  They  are,  in 
reality,  simply  hotbeds  without  artificial 
heat.  When  banked  with  manure  and  pro- 
tected with  mats,  these  frames  will  protect 
tt:nae.rv  plants- at  temperaturesof  15.  or- 20  de- 
grees  below  freezing,  if  of  short  duration, 


SASH-BED  CONSTRUCTION  25 

The  best  frames  are  made  of  cypress  and 
are  joined  at  the  corners  by  means  of  angle 
irons  and  bolts  so  that  they  may  be  easily 
taken  apart  for  storage. 


L  i^S!"^  -tKriH', 


/ 


7 


t»?^: 


Fig.  11. — Coldframe  with  sash  removed.     The  sash  rest  on 
the  crosspieces,  X. 

When  large  numbers  of  frames  are  used  in 
relatively  mild  weather,  they  may  be  very 
cheaply  constructed  by  placing  two  planks 
parallel  to  each  other  and  6  feet  apart.  The 
plank  on  the  north  side  is  12  inches  wide 
and  the  one  on  the  south  side  6  inches  wide. 
When  the  plants  are  removed  the  planks  may 
be  taken  up  and  stored,  or  allowed  to  re- 
main, and  crops  may  be  planted  between 
them. 

In  mild  climates,  coldframes  may  be  util- 
ized for  starting  early  plants  before 
danger  from  frost  is  over,  although  it  is  often 


'.'6 


GREEXIKH'SES 


advisable  to  equip  ihein  wiih  steam  or  hot 
water  pipes,  so  that  they  may  be  heated  in 
ease  of  emergeney.  In  the  north,  eoUl- 
franies  are  used  tor  wintering-  violets,  pansies 
and  other  semi-hardy  plants;  and  farther 
south,  for  wintering  eabbage,  cauliflower  and 
other  plants  which  are  started  in  the  fall. 


Fig  12. — A  cold     or  storaare-pit  with  shelf  for  growing 
violets 

COLD  OR  STORAGE  PITS 

In  almost  every  florist's  or  vegetable  grow- 
er's establishment  there  is  need  for  an  out- 
of-the-way  frost-proof  storage,  to  which  light 
mav  be  admitted  on  occasion.     Such  a  stor- 


ige  may  be  easily  constructed  by  excavating 
a  pit  similar  to  a  hotbed  pit,  but  deeper, 
so  that  the  bottom  will  be  well  below  the 
frost  line.  This  must  be  well  drained  and 
lined  with  a  brick  or  concrete  wall,  which 
should  extend  a  few  inches  above  the  natural 
ground  level  to  prevent  water  running  in  at 
the  top,  but  is  banked  at  the  top  with  soil  or 
manure.  The  pit  may  then  be  covered  with 
sash  and  protected  with  mats  and  shutters 
described  in  a  succeeding  paragraph. 

In  cold  climates  the  pit  is  at  least  5  feet 
deep.  In  very  severe  climates  a  mulch  of 
manure  6  inches  deep  placed  for  a  distance 
of  4  or  5  feet  around  the  pit  before  the  ground 
freezes,  will  effectually  protect  it.  As  the 
normal  winter  temperature  of  the  soil  be- 
low the  frost  line  is  considerably  above  freez- 
ing, coldpits  furnish  excellent  storage  for 
gladioJa,  dahlia  and  similar  plants,  and  also 
for  bulbs  for  winter  forcing.  A  row  of  stor- 
age pits  and  coldframes  along  the  south  side 
of  a  greenhouse  is  of  great  convenience. 
The  house  must  be  provided  with  a  gutter,  or 
the  frames  set  a  foot  or  more  away  from  the 
side  of  the  house  to  guard  against  breakage 


28 


GREENHOUSES 


by  snow  or  ice  falling  from  the  roof.  A  pit 
may  be  attached  to  the  south  side  of  a  dwell- 
ing and  connected  with  the  basement.  When 
the  house  is  heated  by  a  furnace  this  may  be 
easily  heated  with  little  expense,  and  be  used 
for  growing  vegetables  or  flowers  through- 
out the  winter. 


Fig.   13. — Sash-bed  attached  to  basement  of  dwelling 


SASH-BED  CONSTRUCTION 


29 


FORCING  BOXES 

Forcing  boxes  or  plant  forcers  are  small 

coldframes    with    a    single    pane    of    glass, 

which  are  used  to  place  over  individual  plants 

started  early  in  the  spring.     They  are  used 


IQ 

fl 

■Hi 

wmm 

i 

1^ 

IH 

■■ 

Fig.  14. — Types  of  forcing  boxes  or  plant  forcers 

for  protecting  tomatoes,  eggplants,  melons 
and  other  heat-loving  plants,  and  are  re- 
moved as  soon  as  continuous  hot  weather 
arrives.  They  are  used  also  for  forcing  rhu- 
barb, asparagus  and  other  vegetables  in  early 
spring,  and  for  perennial  flowering  plants. 


mcfirj. 


-gfiW  Ji-.:3^i-sifto^ 


Fig.  15. — Forcing  boxes  in  use  on  a  commercial  scaie 


30 


GREENHOUSES 


GABLE  ROOF  SASH-BEDS 

Sometimes    hotbeds    and    coldframes    are 

made  of  two  rows  of  sash  set  so  as  to  form 

a  gable  roof.      They  have  few  advantages 

and    many    disadvantages  when    compared 


Fig,   16. — Gable   roof  sash-bed  heated  by  manure 

with  those  of  the  ordinary  type.  A  few 
years  ago  it  was  quite  common  to  find  sash- 
beds  of  this  kind  with  a  sunken  walk  under 
the  ridge  in  which  the  workman  could  stand, 
the  heat  being  supplied  by  decaying  manure 
the  same  as  in  an  ordinary  hotbed.  Such 
beds  are  convenient  to  operate  in  planting, 
watering  and  cultivating,  especially  in  cold 
weather.  They  are  not  a  profitable  venture 
as  a  rule,  as  heat  can  be  supplied  more  cheap- 
ly from  coal  than  from  manure.  When  an 
investment  has  been  made  in  a  house  of  this 


SASH-BED  CONSTRUCTION  31 

type  it  will  be  found  to  be  economy  to  equip 
^L  with  an  inexpensive  hot  water  system. 

MATS  AND  SHUTTERS 

Hotbeds     and  coldframes,  when  used  in 

climates  or  seasons  in  which  the  temperature 

is  likely  to  fall  much  below  freezing,  must  be 

provided     with     supplementary     coverings. 


^'-^^r      ""'■' 

./^^'   ^ 

-' '               y-^'i^^ 

« '       f                                        ^'i£^^ 

.»-^ 

•  ''^'*                                  ]j^^^ 

'- .'  f ' 

'  fi 

"'■'i^F* 

K " 

t- 

w^ 

'  ■> 

--k:^ 

#, 

Fig.  17. — Rye  straw  mats,  rolled  for  storage 

This  is  especially  true  when  single-light  sash 
are  used. 

Rye  Straw  Mats,  are  extensively  used  for 
this  purpose.  They  were  formerly  made  by 
hand  but  are  now  made  by  machinery  and 
are  fairly  reasonable  in  price.     Each  mat  is 


3S 


GREENHOUSES 


desio-ned  to  cover  two  sash  and  should  be 
6yLy  feet  to  allow  for  turning  over  the  ends 
of  the  sash  to  keep  out  the  wind.  An  ob- 
jection to  straw  mats  is  their  weight,  especi- 
ally when  wet,  and  also  the  fact  that  mice  are 
likely  to  work  in  them  while  they  are  stored 
during  the  summer.  With  careful  handling 
they  will  last  three  or  four  years. 


^ 

p "■ 

-  '*f   wmwmm^mmmm^mmm.^m 

m 

n^M 

^ 

c. 

1 

\msm 

B. 

.♦ 

^    «- 

i' 

.  n 

Fig.  18. — Hot-bed  covered  with  (C)  double  glass  sash; 

(B)  sash  and  straw  mat;  (A)  sash,  straw  mat  and 

shutter 

Burlap  and  Canvas  Mats,  which  are  pad- 
ded with  waste  cotton  and  quilted,  are  easier 
to  handle  than  straw  mats  and  are  somewhat 
more  durable.  Though  usually  thinner  than 
straw  mats,  they  give  practically  as  good 
protection.  They  have  the  added  advantage 
of  requiring  less  storage  space,  and  are  some- 


SASH-BED  CONSTRUCTIOX  33 

times  treated  with  tar  or  other  material  of- 
fensive to  mice. 

Waterproof  Mats,  made  of  heavy  canvas, 
or  sometimes  of  oiled  or  rubberized  fabric, 
seem  to  have  but  little  advantage  over  com- 
mon mats,  except  on  coldpits,  when  they  are 
to  be  used  during  the  entire  winter.  They 
are  relatively  expensive. 

Wooden  Shutters,  3x6  feet  in  size,  made 
of  half-inch  lumber,  are  occasionally  used  to 
place  over  the  mats.  Their  chief  value  is  in 
protecting  hotbeds  when  made  very  early  in 
the  season,  and  for  coldpits. 

Care  of  Sash-bed  Materials. — As  hot- 
beds, coldframes  and  the  like,  are  used  for  on- 
ly a  few  months  during  the  year,  they  are 
likelv  to  be  nes^lected  and  thus  deteriorate 
rapidly.  When  many  are  used,  their  proper 
care  may  spell  the  difference  between  finan- 
cial success  and  failure. 

If  movable  frames  are  used,  they  should 
be  taken  down  and  stored  as  soon  as  the 
plants  are  out.  If  they  are  so  constructed 
that  they  do  not  come  apart,  easily,  they 
may  be  piled  one  above  the  other,  cleaned  and 
painted. 


34  GREENHOUSES 

Sash  should  he  cleaned  stnd  stacked  under 
cover.  Rainy  days  may  be  utilized  in  paint- 
ing them  and  re-glazing  where  necessary.  It 
is  economy  to  re-paint  sash  every  season. 

Mats  must  be  handled  carefully  and  dried 
as  soon  as  possible  after  they  become  v^et  by 
hanging  them  on  a  line  or  fence.  They  must 
be  thoroughly  dry  when  stored  for  the  sum- 
mer and  be  kept  where  mice  cannot  get  to 
them. 


CHAPTER  III 

THE    GREENHOUSE    PROPER— GENERAL 
CONSIDERATIONS 

Location. — Having  determined  upon  the 
geographical  location,  proximity  to  market 
and  fuel  supply  and  the  investment  in  land 
which  the  business  may  be  expected  to  war- 
rant, all  of  which  are  without  the  scope  of 
this  discussion,  the  points  next  to  be  con- 
sidered in  the  location  of  a  greenhouse  are  as 
follows:  (i)  It  should  be  such  that  the  sun- 
light will  not  be  obstructed  at  any  time  dur- 
ing the  day.  The  probability  of  high  build- 
ings being  erected  in  the  immediate  vicinity 
should  be  taken  into  account.  (2)  It  should 
be  well  drained  either  naturally  or  artificially 
and  be  absolutely  free  of  danger  from  floods. 
(3)  It  should  not  be  exposed  to  cold,  bleak 
winds,  as  they  will  quickly  make  their  pres- 
ence known  in  excessive  fuel  bills.  A  wind 
break  of  evergreen  or  other  trees  will  be 
found  ver}^  effective  in  protecting  from  winds 
but  it  will  be  several  years  before  the  trees 
will  be  large  enough  to  be  of  much  benefit. 

35 


3G  GREENHOUSES 

(4)  It  should  be  comparatively  level,  or  gent- 
ly sloping  toward  the  south  or  southeast. 
Hillsides,  if  necessary,  may  be  utilized  by 
building  houses  of  special  design  to  be  de- 
scribed later.  (5)  An  unfailing  supply  of 
water  at  a  reasonable  cost  should  be  assured. 
(6)  If  the  houses  are  to  be  erected  in  connec- 
tion with  other  buildings,  they  should  be  on 
the  south  side  if  possible.  For  most  plants 
the  advantage  of  direct  sunlight  during  the 
whole  day  cannot  be  over-estimated.  (7) 
The  possibility  of  enlarging  the  range  by  the 
addition  of  more  houses  should  not  be  over- 
looked. 

Arrangement. — The  arrangement  will  de- 
pend to  some  extent  on  the  size  of  the  range 
and  the  purpose  for  which  it  is  to  be  used. 
If  for  private  use  only,  convenience  may 
often  be  sacrificed  for  appearance ;  but  for  the 
commercial  house  the  first  thought  in  ar- 
rangement is  for  economy  in  operation. 

For  a  commercial  house  the  following 
points  in  arrangement  should  be  considered: 
(i)  The  direction  in  which  the  houses  are  to 
run.  This  will  be  fully  discussed  in  Chapter 
lY.  (2)  The  distance  between  the  houses. 
This  will  depend  on  the  size  and  height  of  the 


GENERAL  CONSIDERATIONS 


38  GREENHOUSES 

houses  and  on  the  value  of  the  land.  Little 
advantage,  except  in  case  of  heavy  snowfall, 
will  be  gained  over  the  ridge-and-furrow  sys- 
tem (see  Chapter  IV)  by  separating  the  in- 
dividual houses  by  less  than  lo  or  12  feet.  A 
fair  though  not  absolute  rule  is  to  space  the 


CAViUL 


JT, 


L_P ' 


F/amis 


Fig.  20. — Ground  plan  of  range  shown  in  Fig.   19 
—Boiler   room   is   in  basement 

houses  at  a  distance  equal  to  two-thirds  their 
height.  (3)  The  workroom  should  be  con- 
venient to  all  houses  of  the  range,  yet  shade 
them  as  little  as  possible.  (4)  Other  things 
being  equal,  the  boiler  room  should  be  at  the 
lowest  part  of  the  range  in  order  to  secure 
good  circulation.  When  the  houses  are  long 
it  is  usually  best  to' have  it  near  the  center, 
and  to  insure  circulation  by  deepening  the 


GENERAL  CONSIDERATTOXS 


40 


GREENHOUSES 


boiler  pit,  or  in  large  establishments  by  the 
use  of  pumps  or  steam  traps  which  will  be 
discussed  in  the  chapters  on  heating. 

Size  of  House. — There  is  no  authentic  data 
on  the  comparative  efficiency  of  small  and 
large  houses.  The  large  houses  are  relative- 
ly lighter,  but  there  are  other  considerations. 


Sf  «vic£  Building 

AND 

Boiler  /^o/m 


7f 


20 


Fig.  22. — Ground  plan  of  range  shown  in  Fig.  21 

As  a  rule  the  eastern  growers  favor  separate 
large,  high  and  wide  houses  while  those  of 
the  Middle  West  prefer  lower  and  narrower 
connected  houses.  The  present  tendency  is 
to  build  larger  houses  than  formerly.  Of 
i6o  florists  and  vegetable  growers  whom  the 
author  has  consulted,  148  or  88  per  cent,  ex- 
pressed themselves  in  favor  of  houses  rang- 
ing from  24  to  40  feet  in  width.  These  are 
undoubtedly  the  most  popular  widths  at  the 
present   time,   the  leno^th  varying  from    lOO 


GENERAL  CONSIDERATIONS 


41 


42 


GREENHOUSES 


to  500  feet  or  more.  A  discussion  of  the  ad- 
vantages of  high,  wide,  single  houses  and  of 
low,  narrow,  connected  houses  is  given  in 
Chapter  IV. 

Pitch  of  Roof. — The  pitch  of  a  roof  means 
the  degree  of  slant  or  the  angle  of  divergence 
from  the  horizontal.  The  glass  of  the  roof 
not  only  allows  the  light,  heat  and  chemical 


20Ft. 


Fig.  24.  — The  pitch  of  the  roof  is  measured  at  A 

rays  to  pass  through  it,  but  it  also  acts  to 
some  extent  as  a  mirror,  thus  reflecting  a 
part  of  the  rays.  The  amount  lost  by  re- 
flection is  proportional  to  the  angle  of  in- 
cidence. Thus,  if  the  sun's  rays  fall  upon 
the  roof  at  right  angles,  little  or  none  is  lost 
by  reflection;  but  when  they  fall  at  a  less 


GENERAL  CONSIDERATIONS 


43 


44 


GREENHOUSES 


Fig.  26. — Diagram   showing  how  heat   and   light   are   lost 
by  reflection 

angle,  the  amount  reflected  increases  as  the 
angle  of  incidence  increases.  The  amount  of 
the  sun's  energy  lost  by  reflection  when  the 
rays  strike  the  roof  at  various  angles  is 
shown  in  the  following  table. 

Table  showing  per  cent,  of  sun's  energy  lost  when  the 
rays  strike  the  glass  at  different  angles 

Angle  of  ray  Loss  by  reflection 

60  degrees    2.7  per  cent. 


50 
40 
30 
20 
15 
10 


3.4 
5.7 
11.2 
22.2 
30.0 
41.2 


It  is  apparent  that  the  maximum  amount 
of  the  sun's  energy  may  be  secured  by  a  roof 
presenting  to  its  rays  an  angle  of  90  degrees. 
It   is   especially  important  that  the  energy 


GENERAL  CONSIDERATIONS 


45 


of  the  sun  be  conserved  during  the  short  davs 
of  winter.  iVt  its  lowest  period  the  sun  rises, 
in  the  latitude  of  New  York,  scarcely  more 
than  25  degrees  above  the  horizon  at  noon. 
In  order  for  the  roof  to  present  an  angle  of 
CO  degrees  to  the  sun's  rays  at  V'\s  season, 
it  would  need  to  have  a  pitch  of  65  degrees. 


Fig.  26a. — Diagram  s'.owinj  pitch  of  roof  necessary  to 
present  an  angle  of  93  degrees  to  the  sun's  rays  in  winter 

Such  a  roof  would  be  (i)  very  expensive  to 
build  and  maintain,  (2)  would  present  too 
large  an  amount  of  radiating  surface  for  the 
space  covered  and  (3)  would  be  too  high  to 
be  practical  in  houses  more  than  10  or  15 
feet  wide. 

If,  however,  w^e  reduce  the  pitch  to  35  de- 
grees, the  sun's  rays  wall  strike  the  roof  at 
an  angle  of  about  55  degrees  which,  by  refer- 
ence to  the  table,  will  be  seen  to  incur  a  loss 


46  GREENHOUSES 

by  reflection  of  between  2  and  3  per  cent,  on- 
ly. Roofs  of  this  pitch  are  not  diflicult  to 
build,  and  do  not  present  so  large  a  radi- 
ating surface  for  the  area  covered  as  do  roofs 
having  a  pitch  of  65  degrees.  Roofs  having 
a  pitch  of  less  than  26  degrees  are  seldom 
satisfactory  because  the  snow  does  not  clear 
from  them  well  and  they  are  likely  to  leak. 
The  water  of  condensation  which  forms  on 
the  inside  of  the  roof  is  also  likely  to  drip  up- 
on the  plants  when  the  pitch  is  less  than 
about  26  degrees.  When  the  pitch  is  greater, 
the  water  will  usually  follow  down  the  glass 
to  the  edge  of  the  house.  In  even-span  houses 
(see  Chapter  IV)  the  pitch  of  the  roof  varies 
from  26  to  35  degrees,  26  and  32  being  the 
most  popular.  In  some  specially  constructed 
houses  it  is  as  great  as  45  degrees.  Most 
builders  equip  houses  up  to  25  feet  in  width 
with  roofs  having  a  pitch  of  32  degrees,  and 
above  25  feet  with  roofs  having  a  pitch  of  26 
degrees. 

Measuring  the  Pitch. — The  degree  of  pitch 
of  any  even-span  roof  may  be  determined  tri- 
gonometrically  when  the  width  of  the  house 
and  the  height  of  the  ridge  is  known  or  can 
be   measured.       If   the   house  illustrated   in 


GENERAL  CONSIDERATIONS  47 

Fig.  24  is  20  feet  wide  and  the  ridge  is  7  feet 
above  the  eaves,  the  value  of  the  angle, 
known  as  A,  may  be  found  by  the  following 
formula:  Tang.  A=^  equals  Tang.  A~^ 
equals  Tang.  A=.700  or  A=35  degrees. 

Should  the  house  be  of  uneven  span  it  is 
only  necessary  to  measure  the  distance 
corresponding  to  a  (Fig.  24)  and  apply 
the  same  formula.  When  this  is  not  con- 
venient, a  plumb  bob  may  be  dropped  from 
any  part  of  the  roof,  as  at  c,  and  the  distance 
measured  from  the  roof  to  the  point  c\  where 
it  cuts  a  horizontal  line  or  straight  edge  from 
the  point  where  the  roof  joins  the  wall.  This 
distance  may  be  substituted  for  b  in  the 
formula,  and  the  distance  from  c^  to  the  in- 
tersection of  the  roof  and  wall  may  be  sub- 
stituted for  a.  To  avoid  error  the  triangle 
thus  formed  should  be  as  large  as  possible 
and  care  taken  to  see  that  the  lines  are  per- 
fectly vertical  or  horizontal,  as  the  case  may 
be.  By  referring  to  the  following  table  the 
angles  in  degrees  and  minutes  formed  by 
roofs  on  houses  of  various  widths  and  heights 
of  ridge  may  be  quickly  found.  The  figures 
in  ihe  left-hand  column  correspond  to  half 
the  width  of  even-span  houses  or  to  the  dis- 
tance represented  by  a  in  the  above  formula. 


48 


GREENHOUSES 


Table    showing   angle    formed   by  roofs    on    houses    of. 
different  widths  and    heights  of  ridge 


One  ha 

If 

Heigl- 

It  of  rid 

ge  in  feet 

wndth 

4 

5 

6 

7 

8 

9 

10 

in  feet 

O    ' 

O    ' 

o   ' 

O    ' 

O   ' 

o   ' 

0    ' 

6 

32  21 

39  48 

45 

49  24 

.... 

.... 

7 

29  44 

35  32 

40  36 

45 

4849 

.  .  .  . 

8 

26  33 

32 

36  52 

41  11 

45 

48  32 

9 

23  57 

29  3 

2,Z    5 

37  52 

4138 

45 

.10 

26  33 

30  58 

35 

38  39 

4159 

11 

24  26 

28  36 

32  28 

Z6   2 

39  17 

42  13 

12 

22  57 

26  33 

3015 

33  41 

36  52 

39  41 

13 

.... 

24  47 

2818 

3136 

34  42 

37  34 

14 

.... 

.... 

23  12 

26  34 

29  44 

32  44 

35  34 

15 

.... 

25 

28  4 

3100 

33  40 

16 

.... 

.... 

24  13 

26  32 

It  is  perhaps  more  often  desired  to  find  the 
length  of  rafter  necessary  to  form  a,  roof  of 
given  pitch  on  a  house  of  given  width,  than  to 
determine  the  pitch  of  a  house  ah'eady 
erected.  This  may  also  be  solved  trigono- 
metrically.  For  example:  Suppose  it  is  de- 
sired to  know  the  length  of  rafter  necessary 
to  form  a  roof  with  a  pitch  of  35  degrees  on  a 
house  20  feet  wide.  If  the  roof  is  to  be  of 
even  span,  as  shown  in  Fig.  24,  we  will  have 
a  right  angle  triangle,  A  B  D,  the  base  of 
which  is  known  to  be  half  the  width  of  the 
house,  or  10  feet.  If  the  angle  A  is  to  be  35 
degrees  then:  Cosine  A=-^  equals  .81915=  i?. 
Transposing,  X=-7r-or  X=i2.2  feet. 


81915 


GENERAL  CONSIDERATIONS  40 

This  formula  is  also  applicable  to  an  un- 
even span  roof  provided  the  distance  from  the 
point  directly  underneath  the  ridge  to  either 
side  of  the  house  is  known.  For  example :  In 
a  20-foot  three-quarter  span  house,  the  base 
corresponding  to  a  of  the  triangle  A  B  D  in 
Fig.  24  is  either  two-thirds  or  one-third  of 
20  feet,  according  to  which  side  of  the  roof 
we  wish  to  measure. 

In  the  following  table  will  be  found  the 
lengths  of  rafters  required  to  form  roofs  of 
various  angles  on  houses  of  different  widths. 
The  figures  in  the  left-hand  column  corre- 
spond to  half  the  width  of  an  even-span  house 
or  the  horizontal  distance  from  the  eaves  to- 
a  point  directly  underneath,  where  it  is  de- 
sired to  place  the  ridge. 

Table  giving  length  of  rafters  necessary  to  form  roofs  of 
various  angles  on  houses  of  different  widths 


One  ha 

If 

Pitch   in   degrees 

width 

26P 

30° 

32° 

34° 

35° 

40° 

45° 

of  house 

in  fe^ 

et 

LEXGTH  OF 

RAFTERS  IX 

FEET 

6 

6.67 

6.92 

7.07 

7.23 

1.Z2 

7.80 

8.48 

8 

8.90 

9.23 

9.44 

9.65 

9.76 

10.70 

11.31 

10 

11.12 

11.54 

11.79 

12.06 

12.20 

13.05 

14.14 

12 

13.35 

13.84 

14.14 

14.46 

14.64 

15.60 

16.96 

12* 

13.90 

14.43 

17.73 

15.09 

15.25 

16.33 

17.67 

15 

16.80 

17.32 

17.68 

18.09 

18.30 

19.57 

21.21 

20 

22.44 

23.08 

23.58 

24.12 

24.40 

26.10 

28.28 

25 

27.80 

28.86 

35.46 

30.18 

30.50 

32.66 

35.34 

CHAPTER  IV 

GREENHOUSE   ARCHITECTURE 

Architecturally,  the  different  forms  of 
greenhouses  are  named  and  recognized  main- 
ly by  the  style  of  roof. 

Lean-to  or  Shed-roof  Houses. — These  are 
the  simplest  forms  of  greenhouses;  likewise 
the  least  expensive  and  least  satisfactory. 
There  is  little  excuse  for  building  separate 
houses  of  this  type,  but  they  may  be  made  to 
serve  a  useful  purpose  when  erected  against 
the  side  of  a  building  or  against  a  steep  side 
hill.  They  usually  extend  east  and  west, 
with  the  high  wall  to  the  north  and  the  roof 
sloping  toward  the  south.  For  commercial 
purposes  they  are  of  little  value,  as  they  ad- 
mit light  from  only  one  side,  and  but  little 
direct  sunlight,  except  for  a  few  hours  in  the 
middle  of  the  day.  They  may  be  utilized  for 
growing  ferns  and  other  plants  requiring 
little  direct  sunlight,  also  for  starting  early 
plants,  or  as  grape  or  peach  houses,  the  vines 
or  trees  being  trained  against  the  north  wall. 

50 


GREENHOUSE  ARCHITECTURE         51 

Lean-to  houses  not  only  have  the  advant- 
age over  other  types  in  less  first  cost,  but 
also  in  cost  of  maintenance.  They  have  less 
glass  surface  in  proportion  to  the  area  cov- 
ered; hence  there  is  less  breakage,  and  for 
the  same  reason  they  radiate  less  heat.  For 
amateur  use,  especially  when  they  can  be 
erected  against  the  south  side  of  the  dwell- 
ing, they  may  be  built  and  operated  at  small 
cost  and  will  afford  much  pleasure. 

Even-span  or  Span-roof  Houses. — In  these 
houses,  as  the  name  indicates,  the  sides  of 
the  roof  are  of  equal  length.  They  are 
the  most  popular  form,  fully  80  per  cent,  of 
all  houses  of  recent  construction  being  of 
this  type.  They  are  superior  to  the  lean-to 
in  that  they  admit  light  from  two  sides,  and 
also  because  they  may  be  run  either  north 
and  south,  or  east  and  west,  as  may  be  de- 
sired. On  this  point,  however,  practical 
growers  disagree,  some  preferring  the  east 
and  west  arrangement,  others  the  north  and 
south.  Theoretically,  the  points  in  favor  of 
and  against  each  seem  to  about  counterbal- 
ance. They  are  stated  in  the  following 
paragraph. 

The  north  and  south  arrangement  permits 


52  GREENHOUSES 

direct  sunlight  to  fall  on  both  sides  of  the 
house  for  an  approximately  equal  time  dur- 
ing the  day,  thus  giving  all  the  plants  in  the 
house  an  equal  chance.  It  also  permits  the 
workroom  to  be  placed  on  the  north  end, 
where  it  will  not  shade  the  house.  The 
principal  disadvantage  is  that  during  the 
middle  of  the  day,  when  the  sun's  rays  are 
most  potent,  they  strike  obliquely  against 
the  roof  and  much  heat  and  light  is  lost  by 
reflection.  Moreover,  a  large  part  is  cut  off 
by  the  sash  bars  and  rafters. 

In  the  east  and  west  arrangement,  the  di- 
rect sunlight  enters  from  the  south  side  only, 
and  in  the  morning  and  afternoon  strikes  the 
roof  obliquely.  During  the  middle  of  the 
day,  when  it  is  most  effective,  it  strikes  al- 
most at  right  angles,  although  it  is  not  even- 
ly distributed  and  the  plants  on  the  north 
side  of  the  house  receive  much  less  than 
those  on  the  south  side.  This  would  seem  to 
be  a  serious  fault,  but  in  practice  is  less 
serious  than  in  theor.v.  Of  no  s^rowers 
whom  the  author  consulted  on  this  point, 
38  were  in  favor  of  the  north  and  south  ar- 
rangement, 42  were  in  favor  of  the  east  and 
west  and  30  expressed  the  opinion  that  there 
is  little  or  no  difference. 


GREENHOUSE  ARCHITECTURE 


54  GREENHOUSES 

Uneven  Span  Houses. — The  uneven  dis- 
tribution of  light  in  even-span  houses 
running  east  and  west  early  led  to  the 
experiment  of  cutting  off  the  north  one- 
fourth,  so  as  to  make  an  uneven  or  three- 
quarter  span  house.  The  following  advant- 
ages are  claimed  for  these  houses:  (i)  They 
secure  a  more  even  distribution  of  direct  sun- 
light to  all  plants.  (2)  The  north  span  ad- 
mits indirect  light  which  insures  better  re- 
sults than  may  be  secured  from  a  lean-to 
house.  (3)  The  heat  is  more  evenly  distri- 
buted than  in  a  lean-to  house.  They  are 
often  used  in  growing  roses  and  other  plants 
requiring  a  maximum  of  light.  The  con- 
struction of  uneven  span  houses  has  been 
varied  from  time  to  time,  the  general  ten- 
dency being  to  lower  the  north  wall  to  ap- 
proximately the  height  of  the  south  wall. 
This  arrangement  insures  even  better  distri- 
bution of  light  and  does  away  with  the  neces- 
sity of  elevated  benches. 

Uneven  span  houses  are  sometimes  used 
for  growing  lettuce  and  other  vegetables  di- 
rectly on  the  ground  instead  of  in  benches, 
especially  on  sloping  locations.  Modern 
greenhouses  are  so  much  lighter  than  the 
older  types  that  the  advantages  of  the  un- 


GREENHOUSE  ARCl  I ITECTURE 


56  GREENHOUSES 

even  span  house  in  this  connection  are  hard- 
ly worth  considering.  They  are  much  less 
commonly  built  than  formerly.  Uneven  span 
houses  are  sometimes  constructed  with  the 
short  span  to  the  south  with  a  pitch  of  40 
degrees  or  more.  This  brings  the  roof  more 
nearly  at  right  angles  to  the  sun's  rays,  but 
has  little  or  nothing  to  recommend  it. 

Ridge-and-Furrow  Houses. — A  ridge-and 
furrow  house  is  in  reality  simply  two  or  more 
houses  joined  together.  They  may  be  even 
span  or  uneven  span  so  long  as  the  side  walls 
are  of  equal  height.  The  advantages  of  this 
form  of  construction  may  be  mentioned  as 
follows:  (i)  They  are  less  expensive  to  build 
than  separate  houses  of  similar  size,  on  ac- 
count of  the  saving  in  side  walls.  (2)  Not 
only  is  there  a  saving  in  the  number  of  side 
walls,  but  the  interior  walls  may  be  of  cheap 
construction  or  may  be  left  out  entirely,  the 
weight  of  the  roof  being  supported  by  posts 
alone.  (3)  Considerable  saving  is  made  in  la- 
bor because  easy  passage  may  be  had  between 
houses.  (4)  They  conserve  ground  space 
which  is  often  a  considerable  item.  (5)  The 
houses  in  the  center  are  protected  from  wind 
bv  those  on  either  side  and  the  radiation  is 


GREENHOUSE  ARCHITECTURE  57 

thus  reduced.  (6)  Because  there  is  less  ex- 
posed wall  surface,  and  because  the  interior 
houses  are  protected,  they  require  less  fuel 
than  do  separate  houses. 

One  of  the  chief  objections  to  the  ridge- 
and-furrow  system  of  construction  is  the  dif- 


Fig.  29. — Ridge-and-fiirrow  houses  wrecked  by  a  storm 

ficulty  of  removing  snow  from  between  the 
houses  in  regions  subject  to  heavy  snowfall. 
Other  disadvantages  are:  (i)  The  center 
houses  are  shaded  more  or  less,  (2)  side  light 
and  side  ventilation  can  not  be  had,  and  (3) 
soil  and  other  materials  must  be  carried  into 
the  house  from  the  end  instead  of  being  put  in 
at  side  openings.    The  latter  is  a  serious  ob- 


58  GREENHOUSES 

jection  only  when  the  houses  are  long  and 
narrow. 

The  above  remarks  refer  only  to  separate 
and  connected  houses  of  similar  sizes.  At 
the  present  time  there  is  a  difference  of  opin- 
ion as  to  the  advantages  of  the  single  wide 
and   high   house  over  the   small  and   lower 


Fig.  30. — Diagram  showing  that  the  same  amount  of 
roof  is  required  for  several  small,  connected  houses 
as  for  one  large  house  covering  the  same  area  if  the 
pitch  is  the  same.    a+b+c+d+e-f-f=A+B. 

houses  connected  in  the  ridge-and-furrow 
system.  Contrary  to  the  prevailing  notion, 
the  same  amount  of  glass  is  required  by  each 
system  if  the  roofs  are  of  the  same  slant  or 
pitch, 

The  following  advantages  are  claimed  for 
the  large,  single  houses:  (i)  They  are  more 
easily  kept  at  an  even  temperature,  (2)  venti- 
lation may  be  secured  without  subjecting  the 


GREENHOUSE   ARCHTTECTrRE         59 

plants  to  cold  drafts,  (3)  they  are  lighter,  (4) 
they  are  more  easily  cared  for,  (5)  the  light  is 
more  equally  distributed  over  the  whole 
house,  (6)  they  quickly  clear  themselves  of 
snow,  (7)  they  contain  a  larger  volume  of 
air,  and  (8)  they  require  fewer  ventilators 
and  less  ventilating  machinery. 

On  the  other  hand  the  following  disadvant- 
ages are  pointed  out:  (i)  Their  great  height 
makes  them  a  target  for  storms  which  in 
winter  cause  a  greater  radiation  of  heat,  (2) 
they  are  less  easily  re-painted  and  re-glazed, 
and  (3)  the  first  cost  is  greater. 

Notwithstanding  these  objections,  how- 
ever, the  single  house  of  moderate  size  {40  to 
60  feet  in  width)  seems  destined  to  become 
more  and  more  popular. 

Curved-roof  Houses. — Curved  or  curvilin- 
ear roofs  are  now  seldom  seen,  except  on 
conservatories  and  show  houses.  Their  chief 
use  is  for  ornamental  effect.  They  originated 
in  an  attempt  to  so  arrange  the  glass  as  to 
more  perfectly  intercept  the  direct  rays  of 
the  sun,  but  in  practice  they  have  proved  lit- 
tle, if  any,  superior  to  the  straight  roof,  and 
the  expense  is  considerably  greater.  They 
have  never  come  into  general  use  in  a  com- 


60 


GREENHOUSES 


mercial  way.     Curved-roof  houses  are  made 
to  use  either  curved  or  straight  glass. 

Side-hill  Houses. — Mention  has  ah-eady 
been  made  of  one  of  the  forms  of  this  type 
of  house.      Sometimes  a  modification  of  the 


-Diagram  of  a  side-hill  range 

ridge-and-furrow  house  is  utihzed  for  side 
hill  construction.  Side-hill  houses  are  not 
recommended  when  well  drained,  level  land 
may  be  secured,  because  of  the  disadvantage 
of  working  at  different  levels. 

Curved-eave  Houses. — The  shade  caused 
by  eave  plates  and  gutters,  the  difficulty  of 
keeping  them  in  repair  and  their  interference 


GREENHOUSE  ARCHITECTURE 


61 


62  GREENHOUSES 

with  the  clearing  from  the  roof  of  ice  and 
snow  in  winter,  has  led  to  the  adoption  by 
several  firms,  of  the  curved-eave  construc- 
tion. For  small  and  medium-sized  houses 
the  increase  in  light  is  very  noticeable.  In 
larger  houses  it  is  not  so  apparent.  The  ex- 
pense for  glass  is  somewhat  greater  on  ac- 
count of  the  curved  panes  required. 

Circular  Houses. — These  belong  in  a  class 
with  the  round  barn  and  octagonal  house — 
excellent  in  theory  but  impractical  in  use. 
Their  first  cost  and  the  expense  in  mainten- 
ance places  them  without  the  range  of  econ- 
omy as  commercial  houses.  As  ornamental 
houses  in  parks  and  private  places,  and  for 
the  growing  of  tall  tropical  plants  they  have 
their  place. 


CHAPTER    V 

STRUCTURAL  MATERIAL 

Practically  all  the  material,  whether  it  be 
wood  or  metal,  which  goes  into  the  construc- 
tion of  a  modern  greenhouse,  is  milled  or 
shaped  at  the  factory.  It  will  almost  never 
pay  the  prospective  builder  to  attempt  to 
use  material  made  by  any  but  specialists  in 
this  line  of  work.  There  are  several  such 
firms  in  this  country.  Greenhouse  construc- 
tion, then,  so  far  as  the  individual  builder  is 
concerned,  becomes  simply  a  matter  of  choos-  / 
ing  the  kind  of  material  he  desires  to  use;/ 
ordering  it  from  a  responsible  manufacturer 
and  assembling  it  or  placing  it  in  its  proper 
position.;  Most  greenhouse  construction 
firms  have  certain  standard  or  stock  houses 
which  they  ship  complete,  even  including 
nails,  paint  and  putty  if  wanted,  at  a  definite 
stated  price;  and  they  will  erect  thiem  if  it  is 
desired.  ■  They  will  also  design  g^'nd  build  a 
house  or  range  of  houses  to  suj(i  any  given 
condition.  -  ---  —  — -s  - 
'  63 


64 


GREENHOUSES 


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STRUCTURAL  :\IATERLAL 


65 


On  the  other  hand,  there  is  now  such  a 
variety  of  structural  material  to  be  had  that 
it  is  quite  possible,  and  very  often  desirable, 
for  the  buyer  to  design  a  house  according  to 
his  own  ideas  or  to  fit  his  own  special  needs 
or  location;  select  and  purchase  the  materials 
and  erect  it  with  his  own  help  to  suit  his 
special  requirements. 

In  order  to  do  this  it  is  necessary  to  know 
the  names  and  uses  of  the  various  members 
which  go  to  make  up  the  house.  The  prin- 
cipal ones  are  shown  in  Fig.  33  and  are  de- 
scribed in  the  following  paragraphs. 

Glazing-sill  or  Sash-sill. — This  sill  is  bolted 
to  the  top  of  the  wall,  usually  by  bolts  set  into 


Tost 


Wall 


Fig.  34.— Types  of  sills.     A,  B,  C,  and  D  are  wood  sills; 
E  is  cast-iron 

the  concrete,  heads  down,  when  the  wall  is 
built.  It  is  known  as  a  sash-sill  when  the 
house  is  equipped  with  ventilating  sash  along 


C)G 


GREENHOUSES 


the  side  walls  which  close  down  against  it ; 
or  as  a  glazing-sill  when  no  side  ventilating 
sash  are  used  and  the  glass  is  puttied  directly 
against  it.  Sills  are  used  at  the  ends  as  well 
as  at  the  sides  of  the  house.  They  are  of 
various  sizes  and  forms,  and  may  be  of  either 
wood  or  iron.  The  small  sills  are  now  quite 
popular.  Grooves  on  the  under  side  of  the 
wood  sills  prevent  the  water  from  running 
back  between  the  sill  and  the  wall  which 
would  thus  cause  decay. 

Eave  Plate. — This  plate  rests  upon  the  side 
posts  and  forms  the  support  for  the  roof 
members.     It  mav  be  of  either  wood  or  iron. 


Fig.   35. — Types    of   eave    plates.     A,    B,    C,   and   D    are 
wood;  E  is  a  metal  plate 

Gutter. — When  it  is  desired  to  collect  the 
water  from  the  roof,  or  when  houses  are  con- 
nected in  the  ridge-and-furrow  system,  it  i?, 
necessary  to  use  a  gutter  instead  of  an  eave 


STRUCTURAL  MATERIAL 


67 


plate.  Iron  gutters  are  rapidly  displacing 
the  old-fashioned  wood  gutters  as  thev  last 
longer,  and  because  they  need  not  be  so  large 
cind  hence  cast  less  shade. 


Fig.  36. — Types  of  gutters.     A,  and  D  are  wood;  B,  and 

C   are    metal.     C    is    supported   by    two    rows    of    posis 

to    allow    for    a    walk    directly    underneath 

When  gutters  are  used,  they  have  a  fall  of 
at  least  4  inches  for  each  100  feet  in  length. 
This  is  accomplished  by  gradulally  shorten- 
ing the  posts  toward  one  end  of  the  house. 
In  other  words,  the  side  walls  are  higher  on 
one  end  of  the  house  than  they  are  on  the 
other.     On  very  long  houses  the  walls  are 


68 


GREENHOUSES 


Fig.  Zy. — Type  of  gutter 

(a)  used  on  curved- 

eave  houses 


sometimes  so  construct- 
ed that  the  gutter 
slopes  from  the  ends 
each  way  toward  the 
center  and  the  water 
is  carried 
that  point, 
houses  are 
monly  fitted  with  gut- 
ters than  formerly,  on 
account  of  their  inter- 
ference with  the  clear- 
ing of  snow.  A  special 
form  of  gutter  is  used 
on  curved-eave  houses. 


away      at 

Detaclied 

less   com- 


Glazing  Bars. — These  are  bars  which  are 
spaced  along  the  sides  and  ends  of  the  house 
to  which    the    glass    is  \-^y.;y/ , .y/ .^y.yyA 

!t7a 


fastened.  They  are 
much  the  same  as  sash 
bars,  which  will  be 
described  later,  except 
•that  they  are  usually 
somewhat  smaller  and 
are  not  provided  with 
grooves       to       conduct 


...  ^  1  Fig.   38. — Cross   section  of 

the  drip.      Corner  bars  corner  bar 


STRUCTURAL  MATERIAL  -69 

serve  the  same  purpose  as  glazing  bars,  ex- 
cept that  they  are  so  milled  that  they  will 
take  the  glass  from  both  the  sides  and  the 
ends  of  the  house.  One  is  used  at  each 
corner. 

Side  Posts. — These  posts  bear  the  weight 
and  side  strain  of  the  roof.  They  may  be 
of  wood,  gaspipe,  or  structural  irop  or  stedl. 
Their  size  will  depend  on  the  height  of  the 
wall  and  the  width  and  construction  61  the 
house.  Wood  posts  4x4  inches,  2  or  2/^- 
inch  gaspipe,  or  >^  x  3-inch  structural  iron 
of  steel  are  usually  considered  amply  strong 
for  most  houses.  The  gaspipe  and  sted 
posts  are  usually  set  in  concrete  and  mason- 
ry. It  is  best  to  set  the  wood  posts  in  the 
same  manner.  Occasionally  the  structural 
steel  posts  are  bolted  to  iron  sills  which  cap 
a  concrete  or  masonry  wall. 

Sash  Bars. — The  sash  bars  are  among  the 
most  important  of  all  the  members  which  go 
to  make  up  a  greenhouse.  They  must  be 
strong  enough  to  carry  the  weight  of  the 
glass,  yet  be  of  such  form  and  size  as  to 
cast  the  least  possible  shade.  They  are 
of  various  forms  and  sizes.  Bars  made  en- 
tirely of  metal  are  seldom  satisfactory  for 


70 


GREENHOUSES 


the  following  reasons:  (i)  They  are  Hkely  to 
expand  and  contract  considerably  with 
changes  in  temperature,  thus  loosening  and 


A. 


F^ 


£.  K  G. 

Fig.  39. — Types  of  wood  sash-bars.     E,  F,  and  H  are  used 
for  butted  glazing;   G  is  used  for  double  glazing 

often  breaking  the  glass.  (2)  The  extreme 
cold  to  which  they  are  subjected  on  the  out- 
side, as  compared  with  the  warm  tempera- 
ture on  the  inside  of  the  house,  has  a  ten- 
dency to  cause  them  to  warp  and  thus  break 
the  glass  or  cause  it  to  fit  poorly.  (3)  As  all 
metals  are  ready  conductors  of  heat,  much  is 
lost  by  radiation  when  they  are  used.  (4)  In 


STRUCTURAL  MATERIAL 


71 


cold  weather  they  become  so  cold  as  to  cause 
the  moisture  in  the  air  inside  the  house  to 
condense  rapidly  on  them,  which  results  in  a 
large  amount  of  drip.  V^arious  types  of  bars 
have  been  invented  in  an  attempt  to  over- 
come these  difficulties. 


Fig.  40. — Two  types   of  patented  metal   sash-bars 

Wood  sash  bars  are  not  good  conductors 
of  heat  and  condense  but  little  moisture,  but 
moisture  from  the  glass  finds  its  way  to  the 
sash  bars,  so  that  they  are  usually  made 
with  a  groove  or  furrow  on  each  side,  which 
conducts  the  moisture  down  to  the  eaves. 
The  most  common  size  of  wood  sash  bars  is 
iH  K  2y2  inches.  Larger  bars  are  used  for 
special  purposes. 


GREENHOUSES 


Fig.  41. — King  "channel  bars' 


Fig.  42. — "U-Bar"  t\M)e  of  s:'sh-ba 


STRUCTURAL  :\IATERIAL 


73 


Fig.  43. — Gable 

Drip    Gutter.- 

gutter  is  to 
carry  away  the 
water  formed 
b  y  condensa- 
tion inside  the 
house,  whicli  is 
conveyed  to  it 
by  the  sash 
bars.  The  pipes 
leading  from  it 
should  empty 
into  a  cistern 
or  sewer  con- 
nection inside 
the  house,  or  be 


rafter 

-The 


Gable  Bars  or 
Gable  Rafters.  — 
Gable  rafters  are 
used  at  the  ends  of 
the  roof  and  are 
made  so  as  to  re- 
ceive both  the  glass 
of  the  roof  and  that 
of  the  end  of  the 
house.  They  should 
be  large  and  strong 
enough  to  give  ri- 
gidity to  the  gable, 
purpose   of   the    drip 


Fig.    44. — Combination    eave    plate 
and  gutter 


74  GREENHOUSES 

carried  out  below  the  frost  line.  This  is  neces- 
sary to  prevent  freezing,  as  the  greatest  drip 
is  in  the  coldest  weather.  In  some  forms  of 
construction  where  pipe  side  posts  are  used, 
they  are  utilized  as  conductors  of  the  drip 
water,  but  the  saving  thus  accomplished  is 
usually  more  than  counter-balanced  by  the 
early  rusting  out  of  the  posts.  Gutters  are 
made  of  wood,  zinc,  tin  and  galvanized  iron. 

Purlins. — Since  sash  bars  must  be  small 
to  minimize  the  amount  of  shade,  it  is  evident 
that  on  wide  houses  they  cannot  carry  the 
weight  of  the  glass  without  support.  This  is 
accomplished  by  means  of  purlins.  They 
run  lengthwise  of  the  house,  and  are  them- 
selves supported  by  purlin  posts,  by  purlin 
braces,  by  rafters  or  by  some  form  of  truss 
work  to  be  described  later. 

When  ordinary  wood  sash  bars  are  used 
with  glass  i6  inches  wide,  the  maximum  dis- 
tance for  safety  between  purlins  is  not  more 
than  7  feet.  For  example:  If  the  sash  bars 
are  more  than  7  feet  long,  one  purlin  should 
be  used.  If  they  are  more  than  14  feet  long, 
two  purlins  should  be  used,  and  so  on.  This 
distance  decreases  as  the  size  of  the  glass  in- 
creases since  there  are  fewer  bars  to  sustain 
the  same  weight. 


STRUCTURAL  MATERIAL 


75 


Purlins  may  be  of  wood,  gaspipe  or  angle 
iron.  Wood  purlins,  because  of  their  size 
(1^x3  inches),  cast  so  much  shade  that  they 
are  now  little  used.  Purlins  of  i /'4-inch  gas- 
pipe  are  very  satisfactory.  They  are  fast- 
ened to  each  sash  bar,  and  are  supported  by 
posts    or    braces    every    8  feet    along    their 


Fig.  45. — Pipe-strap  for  fastening  sash-bars  to  purlins 

length.  A  very  satisfactory  means  of  fast- 
ening them  to  the  sash  bars  is  by  means  of  a 
U-shaped  pipe-strap.  This  is  placed  under 
the  purlin  and  fastened  to  the  sash  bars  by 
means  of  screws. 

Ridge. — The  ridge  furnishes  a  means  of 
fastening  the  upper  ends  of  the  sash  bars  and 
also  serves  as  a  support  for  the  ventilators. 


76  GREENHOUSES 

It  is  milled  from  a  2  x  4,  or  a  2  x  6-inch  tim- 
ber, the  size  depending"  on  the  width  of  the 
house.  The  form  varies  according  to  the 
method  of  attaching  the  ventilators.  (See 
Chapter  VIII). 

Ventilators. — These  are  fully  discussed  in 
Chapter  VIII. 

Ventilator  Header. — This  is  a  member  up- 
on, which  the  lower  side  of  the  ventilator 
rests.  It  is  cut  and  s:rooved  at  the  factorv 
so  as  to  fit  over  the  sash  bars  and  to  receive 
the  edge  of  the  glass  of  the  roof  in  its  lower 
side. 

Sash  Hanging  Rail. — When  side  ventilat- 
ing sash  are  used  a  special  piece  is  sometimes 
placed  immediately  under  the  eave  plate  or 
gutter,  to  which  the  sash  are  hinged.  This  is 
known  as  a  sash  hanging  rail.  Sometimes 
the  sash  are  hinged  directly  to  the  plate  or 
gutter. 

Weather  Strip. — Because  of  their  construc- 
tion and  the  method  of  hanging,  the  roof 
ventilating  sash  do  not  fit  down  tightly  upon 
the  sash  bars  but  leave  wedge-shaped  open- 
ings. These  are  closed  by  pieces  known  as 
weather  strips. 


STRIT^TURAL  .AFATEIUAI 


^ly 


Rafters. — Their  use  is  now  confined  al- 
most wholh'  to  all-metal  frnme  b.onses  which 
are  discussed  in  Chapter  Yl. 

KIXDS  OF  WOOD 

Three  kinds  of  wood  aie  now  being  used 
in  greenhouse  construction:  Cypress,  cedar 
and  California  redwood.  Of  these  the  first 
two  are  preferred  on  account  of  the  hii^'her 


Fig.  46. — ■  ■  1 '  c  0  k  >■ '  ■  c  .^ !  M-  L  -  - 

cost  of  redwood.  There  is  little  difference 
in  the  durability  of  cypress  and  cedar.  If 
well  framed,  and  if  thoroughly  painted  when 
erected  and  at  least  once  in  two  years  there- 
after, either  will  last  a  lifetime. 

Pecky  c}'press  is  the  heartwood  from  old 
trees.  It  is  full  of  holes  or  ''pecks"  and  is 
often  too  ''shaky"  for  sash  bars  and  other 
small  members,  but  it  is  one  of  the  most  dur- 
able woods  known.  It  is  used  chiefly  for 
benches,  and  in  other  places  where  ordinar}^ 
lumber  decays  rapidly  and  where  great 
strength  is  not  needed. 


.7S 


GREENHOUSES 
FRAMING 


The  woodwork  of  a  greenhouse  always  be- 
gins to  decay  at  the  joints.  For  this  reason 
particular  attention  is  paid  to  the  framing. 
All  joints  are  made  to  fit  closely,  and  before 
putting  together  each  piece  should  be  primed 
with  a  thin  coat  of  lead  paint.     The  joints 


Fig.  47. — The  concentric  system  of  construction 

are  then  given  a  heavy  coating  of  thick  white 
lead  and  put  together  while  the  paint  is  still 
green. 

In  buying  greenhouse  material  it  is  al- 
ways well  to  buy  all  the  woodwork  from  one 
firm  and  to  give  the  concern  a  careful  de- 
scription of  the  house,  together  with  a  draw- 
ing showing  the  width,  height  and  length  of 
the  house,  the  pitch  of  the  roof,  size  of  glass 
to  be  used,  etc.     The  firm  will  then  send  the 


STRUCTURAL  MATERIAL  79 

woodwork  (if  it  is  so  directed)  cut  so  that 
it  may  be  fitted  together  with  but  little 
trouble.  It  should  be  specified,  however, 
that  it  be  well  seasoned  and  not  warped. 
Warped  millwork,  especially  sash  bars  and 
glazing  bars,  are  exceedingly  difficult  to  put 
in  proper  position. 

Some  factories  now  build  their  cave  plates 
and  sash  bars  on  the  concentric  principle, 
which  does  away  with  the  necessity  of  cut- 
ting the  ends  of  sash  bars  differently  for 
roofs  of  different  angles. 


CHAPTER  VI 
FRAMEWORK— METHODS  OF  ERECTING 

The  two  cardinal  virtues  of  a  good  green- 
house framework  are  these :  It  must  be  strong 
and  hght,  and  it  must  cast  but  little  shade. 
The  greatest  advance  in  greenhouse  con- 
struction in  the  last  quarter  of  a  century  has 
been  in  the  framework.  The  old  houses  with 
their  high,  solid  walls  and  heavy  w^oodwork 
are  dingy  and  dark,  when  compared  with  the 
modern  house,  90  per  cent,  of  which  is  glass, 
with  little  or  no  solid  wall  above  ground.  The 
framework  of  these  houses  casts  but  a  frac- 
tion of  the  shadow  produced  by  the  old-style 
frame,  yet  it  is  so  perfectly  rigid  against 
storms  and  snow  that  the  large  panes  of  glass 
are  seldom  broken  or  even  loosened  in  their 
setting. 

Three  general  classes  of  framework  are 
used:  (i)  Wood  frame,  in  which  all  members, 
including  the  posts,  are  of  wood;  (2)  semi- 
iron  frame,  in  which  the  posts,  purlins  and 
purlin  posts  are  of  pipe  or  structural  iron, 

80 


FRA:\rEA\'ORK 


SI 


82  GREENHOUSES 

and  (3)  all-iron  or  all-steel  frame.  In  wood 
and  semi-iron  construction,  rafters  are  sel- 
dom used,  the  sash  bars  performing  this  func- 
tion as  well  as  their  own.  These  forms  have 
the  advantage  of  being  somewhat  cheaper 
than  the  all-metal  frame  construction,  and 
have  the  additional  advantage  that  the  ma- 
terial may  be  cut  and  fitted  on  the  job  by  any 
experienced  workman. 

Wood  frame  houses  cast  more  shade  than 
semi-iron,  and  are  less  durable,  especially  the 
posts.  Semi-iron  houses  are  ver}^  durable, 
and  for  houses  of  medium  width,  are  very 
satisfactory.  Probably  more  houses  of  this 
type  have  been  built  during  the  past  ten  years 
than  of  all  others,  though  the  all-metal  frame 
house  is  now  gaining  in  favor.  This  is 
especially  true  in  the  East,  where  large 
houses  are  coming  into  vogue. 

The  all-metal  frames  are  cut  and  fitted  at 
the  factory  and  are  then  shipped,  knocked 
down,  to  the  place  of  erection.  Most  styles 
of  all-metal  frames  have  rafters,  which  are 
bolted  to  the  side  posts  by  means  of  gusset 
plates  to  form  bents.  The  bents  are  then 
placed  in  position  and  secured  there  by  stays 
and  purlins.  Upon  this  framework  are  then 
bolted    the    wood    sash    bars    and    glazing 


FRAMEWORK  83 

bars.  Metal  sash  bars,  as  before  mentioned, 
seldom  prove  satisfactory.  The  framework 
of  such  houses  is  practically  indestructible, 
and  when  the  woodwork  decays  it  can  be  re- 
placed upon  the  old  framework. 

Usually  the  weakest  part  of  a  greenhouse 
is  the  gable.  It  should  be  well  framed  and 
securely  tied  to  the  purlins  and  other  parts 
of  the  framework. 

METHODS  OF  ERECTION 

Foundations  and  Walls. — In  the  old-style 
high,  solid  wall  greenhouse,  the  wall  was  a 
source  of  much  perplexity,  especially  the 
high  north  wall  of  the  uneven  span  house. 
In  modern  houses,  however,  the  solid  wall  is 
seldom  higher  than  the  top  of  the  benches, 
when  benches  are  used,  or  only  a  few  inches 
above  the  surface  when  plants  are  grown  on 
the  ground.  The  remaining  part  of  the  side- 
wall  is  constructed  of  posts  and  glass,  thus 
giving  more  light.  The  chief  difficulty  with 
the  high,  solid  wall  was  that  the  extremes  of 
temperature  between  the  outside  and  inside 
in  cold  weather  caused  them  to  disintegrate 
rapidly.  This  was  particularly  true  with 
masonry  walls. 


84  GREENHOUSES 

Modern  greenhouse  walls,  for  commercial 
houses,  are  almost  always  of  concrete  and, 
being  low,  give  little  trouble.  Concrete 
blocks  and  hollow  building  tile  are  much 
used.  The  chief  requisite  is  that  the  founda- 
tion shall  reach  below  the  frost  line.  The 
common  practice  is  to  dig  a  trench  12  or 
15  inches  wide  and  3  feet  deep  and  fill  with 
coarse  concrete  to  within  a  few  inches  of  the 
surface.  A  form  is  then  built  of  lumber  to 
the  height  required  and  filled  with  concrete. 
When  the  concrete  has  ''set,"  the  form  is 
taken  away  and  the  sides  of  the  wall  plast- 
ered with  a  cement  mortar.  In  wet,  springy 
soil  it  is  often  desirable  to  lay  a  row  of  drain 
tile  along  the  outside  of  the  wall  and  nearly 
to  the  bottom  of  the  trench,  to  carry  off  the 
water. 

Concrete  walls  are  usually  much  more 
satisfactor}^  than  either  brick  or  stone.  They 
should  be  from  8  to  12  inches  thick,  according 
to  their  height  and  the  side  strain  to  which 
they  are  subjected.  Usually  8  inches  is  suf- 
ficient. In  wet  soils  when  the  boiler  is  placed 
below  the  surface,  it  may  be  necessary  to 
waterproof  the  walls.  For  data  on  concrete 
construction  see  Chapter  XV. 


FRAMEWORK 


85 


Wood  Frame  Houses. — These  are  quite 
satisfactory  when  a  cheap  house  is  wanted 
for  a  comparatively  few  years.  The  side 
posts,  which  may  be  of  cedar  or  cypress,  and 
3x4  inches  in  size,  are  placed  8  feet  apart 
in  holes  3  feet  deep,  and  extend  to  the  height 


Fig.  49. — Plan  for  an  all-^wood  frame  greenhouse 

decided  upon  for  the  side  walls.  They  are 
then  placed  in  alignment  and  the  holes 
poured  full  of  thin  concrete  which  soon  hard- 
ens. The  end  posts  are  similarly  placed,  ex- 
cept that  they  extend  only  to  the  height  pf 
the  bparcjed-up  portion  of  the  w^lh      *   '^  '■-' 


8^  GREENHOUSES 

The  next  step  is  to  place  the  center  posts, 
which  are  usually  2  x  3  or  2  x  4  inches  in 
size.  The  height  of  the  ridge  having 
been  determined  (see  Chapter  III)  these 
posts  are  cut  long  enough  to  allow  the 
lower  end  to  be  set  in  the  ground  about  2 
feet.  They  are  then  put  in  alignment  and 
embedded  in  concrete  the  same  as  the  side 
posts.  The  ridge  is  then  put  in  place  on  top 
of  these  center  posts,  and  the  eave  plate  on 
top  of  the  side  posts,  all  joints  being  set  in 
thick  white  lead  paint. 

The  sash  bars  on  a  house  over  12  feet  in 
width  must  be  supported  with  purlins,  but  it 
is  not  necessary  to  support  them  with  two 
extra  rows  of  posts.  A  perfectly  safe  and 
much  more  convenient  way  is  to  support 
them  with  arms  or  braces  from  the  center 
posts.  This  saves  valuable  ground  space,  and 
the  arms  serve  to  stiffen  the  center  posts  as 
well.  The  length  and  position  of  these  arms 
may  be  determined  by  placing  a  straight  edge 
from  ridge  to  eave  plate  in  just  the  position 
the  sash  bars  will  occupy,  and  nailing  the 
arms  fast,  first  allowing  for  the  thick- 
ness of  the  purlin.  A  good  mechanic  would 
have  determinecj  this  before  the  piosts  were 


FRAAIEWORK  87 

set,  and  have  nailed  the  arms  in  place  before 
raising  them.  The  amateur,  however,  will 
find  it  best  to  put  them  in  place  after  the 
posts  are  up,  or  at  least  to  put  up  a  trial  post 
and  then  make  the  others  after  it  as  a  pattern. 

The  next  step  is  to  nail  on  the  purlin,  and 
then  it  is  ready  for  the  sash  bars,  which  are 
spaced  carefully  so  that  the  distance  from 
rabbet  to  rabbet  is  about  one-eight-inch 
greater  than  the  width  of  the  glass.  This 
can  best  be  accomplished  by  using  a  board 
about  one-eight-inch  wider  than  the  glass, 
and  nailing  the  bars  so  that  the  rabbets  fit 
snugly  against  it  along  their  whole  length. 
The  board  can  then  be  removed  and  used  to 
space  the  next,  and  so  on. 

The  side  and  end  posts  are  next  boarded 
up  to  the  required  height,  using  two  layers 
of  matched  lumber  with  paper  between.  The 
bottom  board,  at  least,  must  be  of  best  qual- 
ity pecky  cypress  to  guard  against  decay. 
Glazing  bars  may  now  be  fitted  along  the 
sides  between  the  eave  plate  and  the  glazing 
sill,  and  between  the  glazing  sill  and  the 
gable  rafters.  Corner  bars  are  placed  at 
each  corner. 


88  GREENHOUSES 

It  will  also  be  necessary  to  make  a  frame 
for  the  door  at  one  end,  and  to  reinforce  the 
gable  glazing-  bars  with  2  x  4-inch  scantling. 
The  house  is  then  ready  for  glazing,  instruc- 
tions for  which  will  be  found  in  Chapter  VII. 

If  C3^press  or  cedar  lumber  is  used  through- 
out, and  if  kept  carefully  painted,  a  house 
like  the  above  should  last  for  fifteen  or 
twenty  years.  The  most  vulnerable  parts  are 
the  posts,  especially  the  portion  where  they 
enter  the  cement.  They  should  be  painted 
regularly  once  each  year  at  this  point.  While 
these  houses  do  not  admit  as  much  light  as 
either  a  semi-iron  or  an  all-iron  frame  they 
will  give  excellent  service.  A  poorly  built 
all-wood  frame  house  is  a  constant  expense 
for  maintenance. 

Semi-iron  Frame  Houses. — Two  methods 
of  framing  a  semi-iron  frame  house  are 
shown  in  Fig.  33.  The  method  shown  on  the 
left  requires  twice  as  many  purlin  posts  as 
the  one  on  the  right.  In  each  case  gaspipe 
is  used.  The  work  of  erecting  differs  but 
little  from  that  described  for  wood  frame 
houses,  except  that  pipe  working  tools  are 
required,  and  a  little  more  skill  is  necessary. 
An  endless  variety  of  fittings  may  be  had 


FRAIMEWORK  89 

for  this  style  of  framing,  which  makes  the 
joining  of  the  frame  work  comparatively 
easy. 

If  it  can  be  procured,  genuine  wrought- 
iron  pipe  is  best  used  instead  of  the  steel  pipe 
now  commonly  sold.      Steel  pipe  rusts  out 


Fig.    50. — Two   methods   of  framing   a   semi-iron   house 
For  others,  see  Fig.  33 

much  more  quickly.  In  this  style  of  house  the 
wall  is  usually  of  concrete  and  may  be  only  a 
few  inches  above  the  surface  of  the  ground, 
or  any  height  desired.  The  side  posts  which 
are  usually  of  2-inch  pipe  are  put  in  position 
and  stayed  before  the  concrete  is  poured  in, 
so  that  when  the  wall  has  set  they  are  per- 
fectly rigid.  Adjustable  brackets  which  fit 
on  the  top  of  the  posts,  and  to  which  the 
eave  plate  or  gutter  is  attached,  make  pos- 
sible the  correction  of  trifling  variations  in 
height. 

Bolts  are  set,  heads  down,  in  the  top  of  the 
wall  w^hile  it  is  soft,  and  project  upward  2  or 
3  inches,     These  are  used  for  fastening  down 


90 


GREENHOUSES  * 


the  sill,  which  is  bored  to  fit  over  the  posts 
and  bolts  and  is  secured  with  nuts.  No 
posts  are  set  in  the  end  walls,  but  the  bolts 
are  set  the  same  as  in  the  side  walls  and  are 
used  for  the  same  purpose. 
In  some  cases  the  posts  are 
set  in  the  ground  and  the  side 
walls  are  constructed  of  two 
layers  of  matched  lumber. 

The  purlin  posts  and  other 
supports  are  put  in  position 
much  the  same  as  in  the  wood 
frame  house,  except  that  in- 
stead of  being  embedded  in 
concrete,  they  are  sometimes 
provided  with  foot  pieces  and 
rest  on  small  concrete  piers. 
Split  malleable  iron  castings 
may  be  had  in  almost  every 
conceivable  form  for  joining- 


Fig.  51. — Struc- 
tural steel  post 
with  board 
wall 


the  frame  together.  These  are 


fastened  by  bolts  and  set  screws,  so  that  it  is 
not  necessary  to  thread  the  pipe.  The  sash 
bars  are  fastened  to  the  pipe  purlins  by 
means  of  U-shaped  clips  or  pipe-straps, 
which  are  secured  to  the  bars  by  means  of 
screws.     Purlins  are  usually  made  of  one  and 


FRAMEWORK  91 

a  quarter-inch  pipe  and  should  ])e  supported 
by  posts  every  8  feet.  Purlin  posts  are  usual- 
ly of  one  and  a  half-inch  pipe  and  braces  of 
one  and  a  quarter-inch  pipe. 

A  well-built   house   of  this   type,   if  well 
cared  for,  should  last  a  lifetime. 


Fig.  52. — Section  of  truss-frame  greenhouse.     The  frame 
is  made  of  gaspipe 

Semi-iron  frames  are  also  made  from  struc- 
tural iron  instead  of  pipe.  They  are  just  as 
satisfactory,  but  are  not  so  easily  worked, 
and  are  usually  cut  and  fitted  at  the  factory. 

All-metal  Frame  Houses. — There  are  three 
types  of  all-metal  framework:  (i)  Those  in 
which  the  roof  is  supported  by  interior  posts, 
much  the  same  as  in  the  wood  or  semi-iron 
houses.      (2)  Those  in  which  the  roof  is  sup- 


92 


GREENHOUSES 


ported  by  a  truss  work,  thus  doing  away  with 
all  interior  posts  (sometimes  known  as  truss- 
frame).  (3)  A  combination  of  the  above 
forms  (known  as  a  combination  truss-frame) 
is  used  in  houses  so  wide  as  to  make  the 
truss-frame  impractical.  This  is  commonly 
used  in  houses  over  40  feet  in  width. 


Fig.    53.^ — Section    of    combination    truss-frame    green- 
house,  172  feet  wide 

As  has  already  been  mentioned,  all-metal 
frame  houses  usually  have  wood  sash  bars 
and  glazing  bars,  but  they  are  not  considered 
as  parts  of  the  framework.  In  these  houses 
the  completed  framework  is  entirely  of  metal, 
the  wooden  members  being  fastened  to  the 
frame  with  bolts  or  screws  and  serving  only 
to  hold  the  glass  in  place. 

In  many  all-metal  frame  houses,  especially 
when  the  roof  is  supported  by  inside  posts,  it 
is  common  to  bolt  an  iron  or  steel  sill  to  the 
wall  and  then  bolt  the  side  posts  to  this  sill. 

A  method  of  erecting  a  modern  combina- 
tion-truss   frame    house,    J'l    feet    wide    and 


FRAMEWORK 


on 


9-i  GREENHOUSES 

nearly  30  feet  high,  to  the  ridge,  is  shown  in 
Fig.  54.  This  work  was  done  entirely  by 
the  owners  and  their  ordinary  help,  without 
any  expert  superintendence  and  at  a  material 
saving  in  cost. 

The  method  was  comparatively  simple. 
The  material  was  first  carefully  distributed 
on  the  site  selected,  and  a  trench  dug  for 
the  foundation.  The  gable  trusses  were 
then  bolted  together,  while  another  gang  of 
men  began  setting  and  guying  the  side  posts. 
The  trench  was  then  filled  with  concrete, 
making  the  side  posts  rigid.  Next  the  in- 
terior posts  were  put  in  place. 

The  first  step  in  putting  up  the  rafters 
was  to  fasten  the  lower  ends  to  the  tops  of  the 
side  posts  loosely,  so  that  they  would  move 
easily,  and  then  raise  the  other  end  into  place 
by  means  of  a  pair  of  "shears,''  made  of  two 
pieces  of  2  x  4-inch  scantling.  When  these 
had  been  securely  bolted  in  place,  the  gable 
truss,  which  had  been  previously  assembled, 
was  swung  into  place  by  means  of  a  block 
and  tackle,  working  from  a  boom.  All 
that  remained  was  to  insert  and  tighten  the 
bolts,  put  the  purlins  in  place  and  move  on 
to  the  next  bent.  The  author  was  told  by 
the  owners  of  this  house  that  it  was  erected 


FRAMEWORK 


95 


96 


GREENHOUSES 


with  greater  ease  than  any  semi-iron  house 
they  had  ever  built. 


Fig.  56. — A  method  of 
erecting  small  all-metal 
frame  houses 


Structural  steel  is  most  largely  used  in 
truss-frame  houses  though  gaspipe  is  now 
quite  popular.  It  is  claimed  for  gaspipe  that 
it  costs  less  than  structural  steel  and  that  it 
casts  less  shade.  Some  objection  has  been 
urged  against  houses  constructed  of  gaspipe 
on  account  of  a  lack  of  rigidity,  but  as  now 
constructed  they  give  very  satisfactory  serv- 
ice. Houses  of  this  type  are  regularly  sup- 
plied by  manufacturers  up  to  54  feet  in  width, 
without  center  supporting  posts.  It  is  prob- 
ably safest  to  have  two  rows  of  supporting 
posts  in  houses  more  than  40  feet  in  width. 


CHAPTER  Vn 

GLAZING  AND  PAINTING 

Greenhouse  glazing  is  an  art  in  itself. 
Most  construction  firms  employ  professional 
glazers.  It  is,  however,  an  art  that  may  be 
readily  acquired.  Many  owners  do  their 
own  glazing  when  occasion  requires,  or  have 
it  done  by  their  ordinary  help.  The  method 
of  glazing  greenhouse  roofs  is  not  the  same 
as  that  used  in  glazing  window  sash.  When 
glazers  from  glazers'  shops  or  hardware 
stores  are  employed,  precaution  should  l^e 
taken  to  see  that  they  understand  the  differ- 
ence. 

Glass. — The  glass  commonly  used  in 
greenhouse  glazing  is  clear,  white,  sheet  or 
window-glass  of  either  A  or  B  grade.  Glass 
with  a  pronounced  green  or  bluish  cast  is  to 
be  avoided,  as  it  obstructs  a  large  part  of  the 
heat,  light  and  chemical  energy  of  the  sun's 
rays. 

Clear,  white  window-glass  ordinarily  ab- 
sorbs about  30  per  cent,  of  these  rays;  green, 

97 


98  GREENHOUSES 

from  40  to  50  per  cent.;  and  blue,  from  50 
to  80  per  cent. 

Glass  known  as  A,  or  first  grade,  is  blown 
from  the  top  of  the  retort  and  is  of  bet- 
ter quality  than  the  B,  or  second  grade, 
which  may  contain  some  foreign  matter  or 
settlings.  Some  of  the  less  regular  panes 
from  the  first  blowing  and  those  containing 
small  air  bubbles  are  also  placed  in  the  B 
grade.  When  it  is  essential  that  the  great- 
est possible  amount  of  light  be  had  and  tight 
glazing  is  necessary,  A  grade  is  used. 

In  most  commercial  constructions  B  grade 
will  give  satisfactory  results.  Poorer  grades 
are  not  satisfactory  for  greenhouse  work. 
The  cost  of  B  grade  is  about  85  per  cent,  of 
the  price  of  A  grade.  Both  A  and  B  grades 
may  be  had  in  two  weights  or  thicknesses, 
known  as  single-thick  and  double-thick. 
Single-thick  runs  about  12  panes  to  the  inch 
and  weighs  from  19  to  21  ounces  per  square 
foot.  Double-thick  runs  about  8  panes  to 
the  inch  and  weighs  from  26  to  29  ounces 
per  square  foot.  Double-thick  is  almost 
always  used  when  the  panes  are  more  than 
8  X  10  inches  in  size.  It  obstructs  but  little 
more  light  and  is  much  more  durable, 
especially  against  hail. 


GLAZING  AND   PAINTING  99 

The  price  of  single-thick  is  from  60  to  70 
per  cent,  of  the  cost  of  double-thick.  Amer- 
ican window-glass  is  the  best  that  can  be 
procured.  The  price  varies  greatly  from  year 
to  year,  probably  more  than  does  the  price 
of  any  other  standard  building  material. 

American-made  glass  is  packed  in  boxes  of 
about  50  square  feet  each.  Foreign  glass 
comes  in  boxes  of  approximately  100  square 
feet  each.  The  number  of  lights  per  box  of 
the  various  sizes  of  American-made  glass  is 
shown  in  the  following  table: 

LIGHTS  PER  BOX   ACCORDING  TO  SIZE 


Lights 

Lights 

Size 

per  box 

Size 

per  box 

7x  9 

114 

14x16 

32 

8x10 

90 

14x18 

29 

8x12 

75 

16x20 

23 

10x12 

60 

16x24 

19 

10x14 

51 

18x18 

22 

12x12 

50 

18x20 

20 

20x14 

43 

18x24 

17 

12x16 

38 

20x20 

18 

14x14 

Z1 

20x24 

15 

Plate  glass  is  seldom  used  in  commercial 
greenhouses,  as  its  cost  is  prohibitive.  It  is 
but  little  better  than  A  grade  window-glass 
for  this  purpose.  In  conservatories  where 
strength  is  more  important  than  transpar- 
encv,  fluted  or  corrugated  glass,  or  glass  in- 


100  GREENHOUSES 

to  which  wire  netting  has  been  blown  is 
sometimes  used.  Ground  or  frosted  glass  is 
occasionally  used  in  palm-houses  or  ferneries, 
where  a  soft,  subdued  light  is  desired.  This 
effect  is  more  commonly  obtained  by  paint- 
ing or  whitewashing  the  clear  glass  and  vary- 
ing the  thickness  of  the  coating  according  to 
the  season  of  the  year. 

Size  of  Glass. — The  size  of  the  glass  varies 
according  to  the  purpose  for  which  the  house 
is  to  be  used,  and  the  taste  and  personal  pref- 
erence of  the  owner.  Where  extreme  light- 
ness is  wanted,  large  panes  are  used  thus 
diminishing  the  number  of  sash  bars.  There 
is,  however,  a  practical  limit  to  the  size.  Glass 
increases  rapidly  in  price  as  the  size  in- 
creases, and  the  large  panes  break  more 
easily.  Moreover,  the  size  of  the  sash  bars 
must  be  increased  to  carry  the  extra  weight, 
and  every  increase  in  their  size  means  more 
shade. 

Of  136  practical  growers  consulted  on  this 
point,  108,  or.  nearly  80  per  cent.,  favored 
either  16  x  20  or  16  x  24-inch  glass  with  the 
longer  edge  parallel  to  the  sash  bar.  That 
is,  the  great  majority  preferred  to  have  the 
sash    bars    spaced    about    16    inches    apart. 


GLAZING   AXD   PAINTING  101 

About  3  per  cent,  favored  i6  x  20-inch  glass 
with  the  shorter  edge  parallel  to  the  sash 
bars,  the  bars  in  this  case  being  20  inches 
apart.  Glass  16  x  20  inches  is  undoubtedly 
the  most  popular  size. 

Methods  of  Glazing. — Practically  all 
methods  of  glazing  make  use  of  putty  to  seal 
the  glass  in  place  and  to  form  an  air  and 
water-tight  joint.  An  exception  is  made 
when  some  forms  of  metal  bars  are  used. 
AVith  these,  felt,  candle  wicking  or  some 
similar  material  is  usually  employed,  and  the 
glass  is  pressed  firmly  against  it  and  kept  in 
place  by  bolts  or  clamps.  Sometimes  a  lead 
facing  is  used  and  the  glass  is  clamped 
against  this  facing. 

The  great  majority  of  houses  are  con- 
structed with  wood  sash  bars  or  bars  having 
wood  cores  with  which  putty  is  supposed  to 
be  used.  With  these  there  are  two  common 
methods  of  setting  the  glass.  It  may  be 
lapped  or  butted. 

Lapped  Glazing. — In  lapped  glazing  the 
lowermost  panes  in  each  run  are  laid  flat 
against  the  bottom  of  the  grooves  in  the 
sash  bar.  Each  succeeding  pane  is  then  laid 
so  that  its  lower  edge  laps  over  the  upper 


102  GREENHOUSES 

edge  of  the  pane  below  it,  in  much  the  same 
VN^ay  that  shingles  are  lapped,  except  that  the 
lap  is  much  narrower.  From  one-eighth  to 
three-eighth  inches  are  allowed  for  lapping, 
the  width  of  the  lap  depending  somewhat  on 
the  size  of  the  glass  and  the  rigidity  of  the 
house  and  roof.  It  should  be  as  narrow  as 
possible,  for  little  light  passes  through  the 
lapped  part  of  the  roof. 


Fig.  57. — Lapped  glazing 

Butted  Glazing. — In  butted  glazing  all 
panes  lie  flat  against  the  bottom  of  the 
grooves  in  the  sash  bars,  and  the  lower  edge 
of  each  glass  rests  directly  against  the  up- 
per edge  of  the  one  below.  This  form  of 
glazing  eliminates  the  lap,  but  it  is  more  dif- 
ficult to  secure  a  tight  roof  than  when 
the  glass  is  lapped.  Roofs  having  a  pitch 
of  less  than  30  degrees  are  likely  to  leak  badly 
when  the  glass  is  butted. 

In  this  form  of  glazing  the  putty  is  some- 
times omitted,  and  the  glass  is  held  in  place 
by  wood  caps  which  fit  over  the  rabbets. 
When  it  is  desired  to  make  an  especially  tight 


GLAZING   AND   PAINTING  103 

roof,  the  upper  and  lower  edges  of  the  panes 
are  sometimes  dipped  in  a  shallow  tray  con- 
taining thick  paint.  They  are  laid  while  the 
paint  is  soft,  and  in  hardening  this  forms  a 
tight,  waterproof  joint.  Zinc  glazing  strips, 
bent  in  the  form  of  a  letter  Z  were  at  one 
time  quite  extensively  used  between  the 
panes  to  make  a  tight  joint.  They  are  still 
used  to  some  extent  between  the  panes  on 
side  and  end  walls. 

Several  advantages  are  claimed  for  butted 
glazing:  (i)  Less  glass  is  likely  to  be  broken 
by  accidents,  for  if  only  one  pane  is  hit,  it 
only  will  be  broken;  while  if  the  panes  are 
lapped,  the  one  immediately  below  is  often 
cracked.  (2)  Less  glass  is  broken  by  the  ac- 
tion of  frosts,  as  there  are  no  laps  in  which 
moisture  can  collect  and  freeze.  (3)  The 
roof  is  lighter,  as  there  are  no  laps  to  ob- 
struct the  sunlight. 

The  chief  disadvantage,  aside  from  leak- 
age, is  the  difficulty  in  repairing  the  roof 
when  a  glass  is  broken,  for  the  pane  must 
be  cut  to  fit  tightly.  In  cold,  stormy 
weather,  this  is  a  slow  and  tedious  process. 

Butted  glazing  is  much  less  used  than 
formerly  among  practical  growers,  which  is 
proof  that,  in  general,  it  is  not  so  well  suited 


104: 


GREENHOUSES 


Fig.  58.— Putty  knife 


for  glazing  roofs  as  is 
lapped  glazing.  More  than 
90  per  cent,  of  the  growers 
interviewed  on  this  subject 
preferred  lapped  glass 
roofs.  On  side  and  end 
walls,  glass  is  quite  com- 
monly butted  with  good 
results. 

Putty. — Putty  is  a  pli- 
able substance  used  in  set- 
ting glass.  The  principal 
ingredients      are     whiting 

and  linseed  oil,  and  its  chief  virtues  are  that 

it  is  easily  worked  and  applied,  and  that  it 

does     not     shrink     on 

drying,  thus  making  a 

water-tight  seal.     For 

greenhouse  use,  putty    <= 

as  bought  in  the  gen- 
eral market  should  be 

mixed  with  pure  white 

lead  at  the  rate  of  one 

part  of  lead  to  five  of 

putty.    This  will  stick 

to  the  bars  and  glass 

much  better  than  wil]  Fig.  50.— Machine  for  dis- 

ordinary  putty.  tributing  putty 


GLAZING  AND   PAINTING 


105 


Putty  purchased  from  dealers  in  green- 
house suppHes  will  not  need  the  addition  of 
lead.  It  should  be  worked  as  soft  as  it  can 
be  handled  in  order  that  it  may  be  easily 
forced  into  all  cracks  and  crevices.  It  is 
applied  with  a  putty  knife  or  with  a  putty 
machine.  The  putty  machine  distributes  the 
putty  rather  more  rapidly  than  can  be  done 
by  hand,  but  it  is  necessary  to  use  a  putty 
knife  in  conjunction  with  it. 

Setting  the  Glass. — The  basic  difference 
between  glazing  greenhouse  roofs  and  glaz- 
ing ordinary  window-sash  is  in  the  method 
of  applying  the  putty.  In  glazing  window- 
sash,  the  putty  is  placed  on  the  outside.  In 
greenhouse  glazing  the  putty  is  placed  in  the 


Fig.  60.- 


-A,    window   glazing;    B,    greenhouse    glazing 
The  putty  is  shown  at  a  and  b 


grooves  in  the  bars  and  the  glass  is  forced 
into  it.  That  which  oozes  up  around  the 
edges  is  scraped  off  and  used  again.  By  this 
method,  little  putty  is  exposed  to  the  air,  but 


106  GREENHOUSES 

the  glass  is  sealed  by  a  thin  film  underneath 
and  along  the  sides  of  each  pane.  This 
method  has  been  developed  because  experi- 
ence has  shown  that  on  roofs  putty  soon 
checks  and  crumbles  away  when  exposed  to 
the  weather  as  in  window  glazing. 

When  glass  is  lapped,  the  following  meth- 
od is  used.  First,  the  sash  bars  should  have 
been  so  placed  that  the  space  left  for  the  glass 
IS  about  one-eighth  of  an  inch  wider  than  the 
glass.  This  provides  room  for  the  "side 
putty."  (For  method  of  spacing  see  page 
87).  Sash  bars  are  usually  primed  when  re- 
ceived from  the  factory.  They  are  given  an- 
other coat  of  paint  after  they  are  put  in 
{)lace  and  are  then  ready  for  glazing. 

Glazing  is  started  at  the  bottom  of  the  run. 
A.  line  of  soft  putty  is  first  placed  in  the  rab- 
bets and  a  pane  of  glass  forced  firmly  into  it 
until  it  is  imbedded  against  the  bar.  A 
groove  is  usually  provided  in  the  plate  to  re- 
ceive the  lower  edge  of  this  glass  to  prevent 
it  from  sliding  down,  but  if  there  is  no  such 
groove,  three  or  four  brads  or  glazing  points 
are  driven  for  the  lower  edge  to  rest  against. 

The  excess  putty  is  then  removed  and  the 
next  glass  forced  firmly  into  place,  so  that 
its  lower  edge  laps  over  and  rests  firmly  on 


GLAZING  AND   PAINTING  lor 

the  top  of  the  first,  and  its  upper  edge  rests 
'on  the  sash  bar.  This  is  fastened  at  the  bot- 
tom with  brads  or  glazing  points  to  prevent 
its  sHding  down.  The  remaining  panes  of 
the  run  may  then  be  placed  in  the  same  man- 
ner, special  care  being  taken  to  secure  the 
uppermost  firmly  in  place  with  glazing 
points.  This  is  necessary  because  it  has  no 
glass  above  it  to  hold  it  in  place,  and  because 
it  acts  somewhat  as  a  key  to  keep  the  others 
in  position. 

It  is  best  to  finish  each  run  from  bottom 
to  top  before  starting  on  a  new  run,  in  order 
that  the  putty  may  cement  into  a  continuous 
mass.  On  high  and  wide  roofs,  however,  it 
is  sometimes  advisable  to  glaze  the  lower 
half  of  the  roof,  then  move  the  scafl:olding 
and  glaze  the  remainder. 

Hov^  to  Estimate  Putty.— The  amount  of 
putty  necessary  to  glaze  a  roof  may  be  esti- 
mated as  follows:  A  pound  of  putty,  when 
applied  by  an  experienced  workman,  will 
reach  about  15  feet  along  one  side  of  a  run 
of  glass  or  about  7>^  feet  along  both  sides. 
To  estimate  the  amount  of  putty,  therefore, 
multiply  the  length  of  the  run  in  feet  by  the 
number  of  runs  and  divide  by  7J^.  This  will 
give  the  number   of    pounds    required.    The 


108 


GREENHOUSES 


amount  required  for  the  sides  and  gable  may 
be  found  in  the  same  way.  An  inexperienced 
workman  will  use  somewhat  more  than  this 
amount  as  there  will  be  more  waste. 

In  glazing  by  the  ''butted  glass"  method, 
putty  may  or  may  not  be  used.  When  it  is 
used,  the  method  is  very  similar  to  that  de- 
scribed above,  except  that  much 
less  is  required,  as  the  panes  are 
crowded  down  to  the  bottom  of 
the  rabbet  along  their  whole 
length  instead  of  only  at  their 
upper  end.  Sometimes  in  glazing 
by  this  method  no  putty  is  used 
until  after  the  glass  is  laid,  and 
then  a  small  quantity  of  liquid 
putty  is  forced  down  along  the 
sides  of  the  glass  with  a  putty 
Pig.  61.  —  bulb.  Usually  when  the  glass  is 
Putty  bulb  batted,  the  bars  are  surmounted 
by  wood  caps.  In  this  system  special  care 
must  be  taken  to  fasten  the  lower  pane,  as 
the  sliding  weight  of  the  entire  run  rests 
against  it. 

Glazing  Points. — Glazing  points  are  used 
to  hold  the  glass  in  place.  They  may  be 
had  in  several  forms  and  sizes.  A  good 
glazing  point  is  easily  driven,  does  not  split 


GLAZIXG   AXD    PAIXTIXG 


100 


the  wood,  offers  as  little  obstruction  as  pos- 
sible to  the  brush  in  painting-  and  does  not 
rust.  Small  sizes  suitable  for  glazing  win- 
dow-sash in  wdiich  the  putty  is  placed  on 
tlie  outside  are  too  small  for  greenhouse  glaz- 
ing. Zinc  points  of  various  forms  have 
been  frequently  used  l^ecau^^e  of  their  free- 
dom from  rust.  The  triangular  point  is  prob- 
ably the  most  popular  of  the  zinc  points,  and 


Fig.  62. — Types  of  glazing  points 

is  quite  commonly  used  in  window  glazing. 
It  is  not  well  suited  to  greenhouse  glazing 
on  account  of  the  difficulty  of  fastening  the 
panes  of  glass  with  it  so  that  they  will  not 
slide  down  the  roof. 

Probably  the  most  used  point  in  green- 
house glazing  is  the  double-pointed  staple. 
This  is  easily  driven  and  when  galvanized  is 
not  subject  to  rust.  The  best  form  of  this 
type  of  staple  is  bent  to  an  angle  in  the  cen- 
ter, so  as  to  fit  over  and  hold  the  lower  edge 


110 


GREENHOUSES 


of  the  pane  from  slipping  lengthwise,  as  well 
as  to  hold  it  down  in  place. 

In  lapped  glazing  only  two  double  points 
are  used  for  each  pane,  that  is,  one  at  each 


Fig.  63. — Glazing  with   double  glazing  points 

lower  corner.  The  upper  edge  is  kept  in 
place  by  the  bottom  of  the  pane  above  it.  Ad- 
ditional points  are  required  for  the  lower- 
most and  topmost  panes  in  each  run,  and  as 
some  will  be  lost  and  destroyed,  it  is  well  to 


GLAZING   AND   PAINTING 


m 


figure  on  three  points  for  each  pane.  An 
average  of  five  of  the  small  single  points  will 
be  required  for  each  pane. 


Fig.   64. — Glazing   with   single   glazing   points 

Precautions. — All  sheet  glass  is  slightly 
curved,  a  condition  caused  by  the  process  of 
manufacture.  When  seconds  or  B  grade 
glass  is  used,  it  v^ill  sometimes  be  found  that 
the  panes  will  be  so  much  curved  as  to  make 


112  GREENHOUSES 

it  difficult  to  lay  a  tight  roof.  If  this  trouble 
is  experienced,  it  will  be  of  advantage  to  sort 
the  glass  and  lay  out  each  run  on  a  smooth 
floor,  placing  the  panes  having  a  similar  de- 
gree of  curvature  in  the  same  run.  By  doing 
this  a  tighter  and  more  satisfactory  roof  can 
be  laid. 

Theoretically,  the  glass  will  resist  more 
pressure  if  it  is  "placed  so  that  the  curve  will 
be  up,  that  is,  so  that  it  will  present  a  convex 
surface  to  the  weather.  If,  on  the  other 
hand,  it  is  placed  so  as  to  present  a  concave 
surface  to  the  weather,  the  water  will  have 
a  tendency  to  flow  away  from  the  sash  bars 
and  putty  to  the  center  of  the  runs.  In  ac- 
tual practice,  these  are  relatively  unimport- 
ant considerations,  but  all  glass  in  the  same 
run  should  have  approximately  the  same 
curvature. 

Liquid  Putty. — This  is  sometimes  used  for 
sealing  cracks  in  old  glazing  or  in  glazing  by 
the  "butted"  method.  It  may  be  made  as 
follows:  Take  equal  parts  by  measure  of 
white  lead,  putty  and  boiled  linseed  oil. 
First,  mix  the  putty  and  oil  thoroughly  and 
then  add  the  lead.  If  it  becomes  too  thick, 
thin  with  turpentine. 


GLAZING   AND   PAINTING  113 

Substitutes  for  Glass. — On  hot  l^ecls  and 
coldframes  and  sometimes  on  temporary 
greenhouses,  some  transparent  material 
other  than  glass  is  used.  The  reason  for  this 
is  that  glass  is  both  expensive  and  heavy  to 
handle.  The  most  common  substitutes  are 
cloth  and  paper  treated  so  as  to  make  them 
w^aterproof  and  semi-transparent.  Some- 
times a  firm  but  lightweight  white  cotton 
cloth  is  used  with  no  treatment,  but  it  does 
not  admit  light  enough  to  permit  satisfactory 
growth  of  plants  for  any  length  of  time. 

Paper  can  seldom  be  used  for  more  than 
one  year.  Cloth  may,  with  care,  be  used  for 
several  seasons.  The  best  results  are  secured 
by  stretching  the  cloth  or  paper  on  rigid 
frames  or  sash  on  which  wires  have  been 
drawn  tightly  across  at  frequent  intervals  to 
serve  as  supports.  The  author  has  had  good 
success  by  simply  painting  the  cloth  or  pa- 
per, after  stretching  it  over  the  frames,  with 
pure,  light,  boiled  linseed  oil.  Bailey,  in  the 
'Tarm  and  Garden  Rule  Book,"  gives  the  fol- 
lowing recipes: 

(i)  Paste  stout,  but  thin  Manilla  wrap- 
ping-paper on  the  frames.  Dry  in  a  warm 
place  and  then  wipe  the  paper  with  a  damp 
sponge  to  cause  it  to  stretch  evenly.     Dry 


lU  GREENHOUSES 

again  and  then  apply  boiled  linseed  oil  to 
both  sides  of  the  paper  and  dry  again  in  a 
warm  place. 

(2)  Dissolve  iH  pounds  of  soap  in  a  quart 
of  water;  in  another  quart  dissolve  i>^  ounces 
of  gum  arabic  and  5  ounces  of  glue.  Mix 
the  two  liquids,  warm,  and  soak  the  paper, 
hanging  it  up  to  dry.  Used  mostly  for 
paper. 

(3)  Take  3  pints  pure  linseed  oil,  i  ounce 
sugar  of  lead,  4  ounces  of  white  resin.  Grind, 
and  mix  the  sugar  of  lead  in  a  little  oil,  then 
add  the  other  materials  and  heat  in  a  kettle. 
Apply  hot  with  brush.      Used  for  muslin. 

PAINTING 

Probably  few  other  structures  require  as 
careful  or  as  frequent  painting  as  do  green- 
houses. This  is  due:  First,  to  the  moist  con- 
dition of  the  air  in  the  house,  which  favors 
the  decay  of  the  wood ;  and  second,  to  the  dif- 
ference in  temperature  between  the  outside 
and  inside  of  the  house,  which  often  causes 
excessive  contraction  and  expansion  of  the 
structural  material.  It  is  especially  important 
that  all  joints  in  the  framework  be  thorough- 
ly coated  when  they  are  put  together,  and 
that  they  be  well  painted  in  order  to  prevent 


GLAZING   AXD   PAINTING 


11. 


moisture  from  entering.  As  a  rule,  green- 
houses should  be  painted  one  coat  both  inside 
and  outside  every  second  year,  and  inside 
portions  which  are  especially  exposed  to 
dampness  and  shade  should  be  painted  every 
year,  care  being  taken  to  see  that  they  are 
perfectly  dry  when  painted.  Nothing  has 
yet  been  found  which  will  excel  pure  white 
lead  and  oil  with  a  turpentine  dryer  for  this 
purpose.* 

For  the  outside  the  mtense  white  may  be 
softened  by  the  addition  of  a  little  lampblack 
or  other  coloring  material,  but  for  the  inside, 
colors  are  avoided,  as  they  have  a  ten- 
dency to  absorb  light.  Pure  white  is  un- 
doubtedly best  for  interior  painting. 

Greenhouse  woodwork  when  received  from 
the  factory  has  usually  been  given  a  priming 
coat.  By  special  arrangement  it  is  often  pos- 
sible to  have  it  treated  in  a  bath  of  hot  lin- 
seed oil  or  creosote.     The  latter  will  make  it 

*On  this  point  commercial  greenhouse  builders  do  not 
agree.  One  of  the  largest  firms  in  the  country  uses 
a  paint  containing  10  per  cent,  of  French  zinc  and 
finds  it  the  most  satisfactory  paint  they  have  ever 
used.  Another  well-knov^n  firm  after  experimenting 
with  lead  and  zinc  in  varying  proportions  has  gone 
back  to  pure  lead.  The  tendency  of  zinc  paints  is 
to  crack  and  peel,  and  of  pure  lead  paints  to  become 

•       chalky.  •        ' 


116  GREENHOUSES 

almost  proof  against  decay,  but  since  the 
joints  must  be  coated  with  a  thick  paint 
when  the  house  is  erected,  and  as  the  wood- 
work is  preferably  white  in  order  to  make  the 
house  as  light  as  possible,  the  extra  expense 
involved  is  hardly  warranted.  Creosote  also 
has  a  somewhat  poisonous  effect  on  some 
greenhouse  plants. 

If  the  woodwork  has  not  been  primed 
when  received,  it  is  preferably  so  treated  be- 
fore it  is  erected.  Either  pure,  thin  linseed 
oil,  or  a  mixture  of  oil  and  yellow  ochre  is 
used  for  this  purpose.  As  soon  as  erected, 
the  whole  framework  is  painted  inside  and 
out  before  glazing.  After  glazing  another 
coat  is  applied.  Because  of  the  frequent 
painting  necessary,  it  is  seldom  advisable  at 
the  time  of  erection,  to  apply  more  than  two 
coats  in  addition  to  the  priming  coat. 

Paints  for  Iron  Work. — Ordinary  paints 
which  are  used  for  wood  may  also  be  used  on 
most  unpolished  metals.  The  oxidization  of 
iron  and  steel,  however,  is  likely  to  stain 
white  paint,  unless  these  metals  are  first 
given  a  coating  to  prevent  it.  A  good  paint 
for  this  purpose  may  be  made  by  melting  to- 
gether three  parts  of  lard  and  one  part  of 
powdered  resin.    This  is  brushed  on  in  a  thin 


GLAZING  AND   PAINTING  11 ; 

layer  while  hot.  As  soon  as  it  is  dry,  ordin- 
ary white  lead  paint  may  be  applied  with 
little  danger  of  its  becoming  discolored. 
Shellac  may  also  be  used  for  the  same  pur- 
pose. 

Hot  water  and  steam  pipes  cannot  well  be 
painted  with  lead  and  oil  paints  on  account 
of  the  action  of  the  heat.  One  of  the  most 
satisfactory  treatments  for  heating  pipes  is 
to  paint  them  with  the  so-called  ''aluminum" 
radiator  paint.  This  is  light  in  color  but 
rather  expensive.  Paints  which  dry  with  a 
glazed  surface  are  said  to  interfere  with  the 
radiating  properties  of  heating  pipes.  A 
dull  drying  black  paint  sometimes  recom- 
mended for  this  purpose  is  a  mixture  of  lamp- 
black and  turpentine,  to  which  linseed  oil  is 
added  not  to  exceed  a  fourth  of  the  bulk  of 
the  mixture. 

Amount  of  Paint  Required. — This  varies 
according  to  the  kind  and  condition  of  the 
surface  to  be  painted,  and  to  some  extent 
with  the  kind  of  paint  used.  Painters  usually 
figure  that  a  gallon  of  mixed  paint  will  cover 
-50  to  300  square  feet  of  white  pine  or  cy- 
press the  first  coat,  and  350  to  400  square 
feet  the  second  coat, 


118  GREENHOUSES 

A  general  rule  for  determining  the  amount 
required  is  as  follows :  Divide  the  number 
of  square  feet  of  surface  to  be  painted  by  200, 
the  result  will  be  the  number  of  gallons  of 
liquid  paint  required  to  give  two  coats. 

Another  is:  Divide  the  number  of  square 
feet  by  18.  The  result  is  the  number  of 
pounds  of  pure,  ground,  white  lead  necessary 
for  three  coats. 

Shading. — During  the  summer  the  heat 
becomes  so  intense  in  a  greenhouse  that  some 
shade  must  be  given  if  plants  are  to  be  grown 
satisfactorily.  This  may  be  accomplished  by 
the  use  of  muslin  curtains  in  the  inside  of 
the  house  or  by  lath  screens  laid  upon  the 
roof.  The  most  common  method  in  com- 
mercial houses  is  to  apply  some  kind  of  a 
coating  to  the  outside  of  the  glass  which  will 
be  washed  off  by  the  late  fall  rains.  Some 
form  of  whitewash  is  most  satisfactory. 

The  author  prefers  a  wash  made  of  fresh- 
ly-slaked stone  lime  and  water,  to  which  is 
added  one  part  of  common  salt  to  four  parts 
of  lime.  The  salt  is  added  after  the  lime  is 
slaked.  This  is  then  strained  and  applied 
with  a  spray  pump.  It  is  usually  necessary 
to  apply  this  two  and  often  three  times  dur- 


GLAZING   AND   PAINTING  110 

;     ing   the   summer,   but   it   comes   off   readily 
through  the  action  of  the  fall  rains  and  frosts 

•    and  seldom   requires   the   use   of  the  scrub 
brush. 

Another  paint  sometimes  used  is  com- 
posed of  white  lead  and  gasoline,  just  enough 
lead  being  used  to  make  a  milk-colored 
liquid.  This  may  be  applied  with  a  brush  or 
with  a  spray  pump.  It  adheres  much  better 
than  the  wash  mentioned  above,  but  is  open 
to  the  objection  that  it  is  sometimes  neces- 
sary to  do  considerable  hand  work  to  remove 
it  in  the  fall. 

A  third  wash  sometimes  recommended  is 
made  as  follows :  Slake  a  half  bushel  of 
stone  lime.  Strain  and  add  a  brine  made  of 
one  peck  of  salt  in  enough  warm  water  to 
fully  dissolve  it.  Then  add  three  pounds  of 
rice  flour,  and  boil  to  a  paste.  Then  add  a 
half  pound  of  whiting  and  one  pound  of  glue 
dissolved  in  warm  water.  Mix  thoroughly 
and  let  stand  for  a  few  days,  thin  with  water, 
and  apply.  This  is  the  whitewash  com- 
monly used  for  painting  fences  and  build- 
ings and  is  very  adhesive.  For  greenhouses 
it  is  applied  in  a  very  thin  coat. 

Brackets. — In    glazing    and    painting    the 


120 


GREENHOUSES 


outside  of  a  roof,  a  common  means  of  sup- 
port for  the  workman  is  a  plank  supported 
by  brackets  resting  on  the  sash  bars  or  on 
every  other  sash  bar. 

Glazing    Ladder. — Another    device    used 
more  in  painting  than  in  glazing  is  a  ladder 


Fig.  65. — Glazing  ladder  used  in  glazing  and  painting- 
made  b}^  nailing  cleats  on  one  side  of  a  plank 
for  foot  holds,  and  on  the  other  side  longer 
cleats  so  that  they  will  rest  across  at  least 
two  sash  bars  and  thus  distribute  the  weight. 
The  ladder  is  held  in  place  by  hooks  which 
reach  over  the  ridge. 


CHAPTER  VIII 

VENTILATION  AND    VENTILATING 
MACHINERY 

Greenhouse  ventilation  has  not  yet  been 
worked  out  with  the  same  care  and  precision 
as  has  the  ventilation  of  dwellings,  public 
buildings,  or  even  barns  for  the  use  of  live 
stock.  On  the  other  hand,  greenhouses  are 
seldom  or  never  built  without  some  special 
attention  being  given  to  the  question  of 
ventilation,  whereas,  dwellings  and  even 
public  buildings  are  often  erected  without 
any  reference  whatever  to  this  important 
subject. 

This  anomaly  may  be  partly  explained  by 
the  following  facts:  (i)  The  transpiration  of 
plants  is  not  so  well  understood  nor  is  it  so 
easily  measured  as  is  the  transpiration  of  ani- 
mals. (2)  Windows  are  necessary  in  dwell- 
ings and  public  buildings  to  admit  light  and 
the}^  may  be  utilized,  when  necessary,  to  pro- 
vide ventilation.  (3)  In  greenhouses,  ventila- 
tion is  not  only  provided  for  the  purpose  of 

121 


122  GREENHOUSES 

maintaining  a  supply  of  fresh  air,  but  is 
utilized  as  a  method  of  controlling  tempera- 
ture and  humidity.  (4)  Greenhouses,  be- 
cause of  their  transparent  roofs,  are  much 
more  liable  to  sudden  or  violent  changes  in 
temperature  (especially  in  days  of  alternate 
clouds  and  sunshine)  than  are  dwellings,  and 
the  necessity  for  ventilation  in  order  to 
equaHze  the  temperature  is  evident.  (5) 
Greenhouse  plants  are,  as  a  rule,  particular- 
Iv  sensitive  to  cold  drafts,  and  ventilation 
cannot  be  left  to  the  indiscriminate  opening 
of  doors. 

Systems    of     Greenhouse    Ventilation. — 

There  can  hardly  be  said  to  be  any  well  de- 
fined systems  of  greenhouse  ventilation,  as 
compared  with  the  so-called  systems  of 
ventilation  for  public  buildings.  Greenhouse 
ventilation  rests  on  the  principle  that  warm 
air  has  a  tendency  to  rise,  and  since  the  air 
within  the  greenhouse  is  considerably  warm- 
er than  that  outside,  during  both  summer 
and  winter,  the  question  of  changing  the  air 
presents  no  serious  problem.  It  is  only 
necessary  to  provide  a  means  for  the  warm 
air  to  escape.  The  copier  air  from  the  out- 
side  easily    finds    its  .way    into    the    house 


VEXTILATIXG 


123 


through    the   numerous   small   openings   be- 
tween the  panes  of  glass. 

Side  Ventilation. — Side  ventilation  is  of 
Httle  service,  except  during  the  summer 
months,  as  the  opening  of  these  ventilators 
in  winter  would  expose  the  plants  to  a  direct 


Fig.  66.— Greenhouse  showing  A,  side  ventilators; 
B,  overhead  or  roof  ventilators 

current  of  cold  air  which  would  prove  fatal. 
Side  ventilating  sash  are  usually  hinged  at 
the  top  and  open  outward  and  upward. 
Probably  less  than  50  per  cent,  of  the  com- 
mercial houses  in  the  country  are  equipped 
with  side  ventilation,  though  it  is  often  con- 


124  GREENHOUSES 

venient  in  spring  and  summer.  An  in- 
genious method  is  sometimes  employed  in 
conservatories  whereby  the  air  is  taken  in 
from  below  the  benches  and  is  warmed  by 
passing  over  the  heating  pipes.  Thus  the 
danger  of  injury  to  the  plants  is  greatly  less- 
ened. There  is  no  evidence  to  show  that 
there  is  any  special  benefit  to  be  derived  from 
these  ventilators  (Fig.  6y), 

Overhead  Ventilation. — During  the  winter 
practically  all  the  ventilation  of  greenhouses 
is  accomplished  by  means  of  overhead 
ventilators  set  in  the  roof  at  or  near  the 
ridge.  These  ventilators  are  in  the  form  of 
sash  hinged  on  the  outside,  and  may  be 
closed  down  tightly  over  the  sash  bars  or 
opened  to  any  degree  desired.  As  the  warm 
air  naturally  rises,  the  opening  of  these 
ventilators  allows  the  warmest  air  of  the 
house  to  escape,  and  fresh  cool  air  to  filter 
in  through  the  crevices  between  panes  of 
glass  without  causing  excessive  drafts. 

Experience  shows  that  these  ventilators 
need  to  be  relatively  narrow  and  practically 
continuous  along  the  whole  length  of  the 
house,  rather  than  intermittent,  as  the  pres- 
ence of  occasional   large  openings   is   more 


VEXTILATTXr. 


^r• 


126  GREENHOUSES 

likely  to  cause  drafts  of  cold  air.  They  are 
preferably  glazed  with  glass  of  the  same 
width  as  used  for  the  roof  and  they  should 
be  placed  so  that  the  bars  of  the  sash  will 
be  directly  over  the  sash  bars. 

Size  of  Ventilators. — No  definite  rule  can 
be  given  as  to  the  size  of  ventilators,  as  so 
much  depends  on  the  location  and  arrange- 
ment of  the  house,  the  kind  of  plants  to  be 
grown,  etc.  Experience  has  shown  that 
where  the  ventilators  are  continuous  along 
the  entire  length  on  both  sides  of  the  roof, 
the  following  sizes   are  sufficient. 

Size    of   house  Width    of    ventilating    sash 

Up  to  40  feet  wide  24  inches 

Above   40   feet   wide  30  inches 

This  is  the  rule  followed  by  most  green- 
house builders. 

Methods  of  Hanging  Sash. — Ventilating 
sash  may  be  hung  so  as  to  open  either  at  the 
top  or  bottom;  that  is,  they  may  be  hinged 
at  the  lower  side  so  as  to  open  out  and  away 
from  the  ridge,  or  they  may  be  hinged  at  the 
ridge  so  as  to  open  upward  from  the  lower 
side.  Both  methods  have  their  advantages 
and  disadvantages.  Sash  opening  at  the 
ridge  have  the  advantage  that  the  air  will 


VEXTILATIXG 


127 


escape  more  rapidly  when  the  ventilators 
are  opened,  as  there  is  hut  little  ohstruc- 
tion  and  the  opening  is  at  the  highest  part 
of  the  house.  There  is  also  less  tendency, 
when   ventilators   are   used   on   one   side   of 


Fig.  68. — Two  methods  of  hanging  ventilator  sash 

the    roof    only,    for    unfavorable    winds    to 
blow  directly  into  the  house. 

The  practical  disadvantages  of  this  meth- 
od of  hanging  is  that  the  ventilator  sash 
are  more  likely  to  be  torn  off  by  severe  storms 
than  when  hinged  at  the  top,  and  also  that 
it  is  more  difficult  to  prevent  leakage  at 
the   ridge.     The   prevailing   tendency  is   to 


128  GREENHOUSES 

hinge  the  sash  at  the  ridge  and  in  houses  30 
feet  wide  or  more  to  provide  ventilators  on 
both  sides  of  the  roof. 

Operating  Machinery. — Since  the  ven- 
tilating sash  are  placed  at  the  highest  part 
of  the  house,  and  as  it  is  necessary  to  change 
the  size  of  the  opening  several  times  a  day, 
it  is  obvious  that  it  is  highly  desirable  that 
some  method  be  provided  by  which  they  may 
all  be  opened  and  closed  from  some  point 
convenient  for  the  operator.  This  is  accom- 
plished by  means  of  various  types  of  sash- 
operating  machiney. 

The  essential  features  on  which  most 
types  of  ventilating  machinery  depend  are 
as  follows:  (i)  A  horizontal  shaft  firmly 
fastened  near  the  line  of  ventilating  sash; 

(2)  a  system  of  gearing,  by  which  power  ap- 
plied at  a  point  convenient  to  the  operator 
may  be  transmitted  to  and  rotate  this  shaft; 

(3)  arms  or  levers  attached  to  the  shaft  and 
also  to  the  sash,  and  so  arranged  that  the 
sash  are  raised  or  lowered  when  the  shaft 
is  rotated. 

Shafting. — The  shafting  generally  used  is 
one  inch  or  one  and  a  fourth  inch  gaspipe. 
The  lengths  are  either  riveted  or  clamped 


VEXTILATIXG 


120 


together  l)y  special  couplings  so  that  the 
shaft  will  be  perfectly  rigid.  A  method 
sometimes  used  is  to  screw  the  lemrths  of 
pipe  into  an  ordinary  sleeve  coupling  as 
far  as  they  will  go;  drill  a  hole  through  each 
end  of  the  coupling  and  pipe,  and  rivet  all 
together  with  tight-fitting  rivets.  This 
method  is  less   satisfactory,  however,   than 


Fig.  69. — Alalleable  iron  shaft  couplings 

the  use  of  split  malleable  iron  castings  sev- 
eral forms  of  which  are  to  be  had.  These 
castings  are  longer  and  stronger  than  the 
usual  sleeve  coupling  and  they  thus  have  a 
firmer  grasp  on  the  pipe. 

They  usually  have  pins  or  lugs  cast  in 
the  inside  which  fit  into  holes  drilled  in  the 
pipe  at  the  proper  positions,  and  the  two 
parts  are  clamped  tightly  in  place  by  means 
of  bolts.     A  special  advantage  of  this  meth- 


130 


GREENHOUSES 


od  of  coupling  is  that  the  shafting  may  be 
put  up  in  sections  and  clamped  together  after 
being  put  in  place.  Square  or  round,  solid 
shafting  is  sometimes  used,  but  it  has  less 
torsional  or  twisting  strength,  weight  for 
weight,  than  does  good  wrought-iron  or 
steel  pipe.  Wrought  pipe  comes  in  two 
weights,  standard  and  extra  heavy.  It  is 
safe  to  use  the  different  sizes  and  strengths 
as  follows :  Shafts  up  to  50  feet  in  length, 
I  inch  standard  strength;  shafts  up  to  75 
feet  in  length,  40  feet  of  i  inch  extra  heavy, 
and  35  feet  standard  strength;  shafts  up  to 
125  feet  in  length,  iH  inch  all  extra  heavy. 

Shaft  Hangers. — The  shafting  is  held  in 
place  by  means  of  hangers.     These  hangers 


Fig.  70.— Shaft  hangers 

may  be  fastened  to  the  rafters,  to  the  sash 
bars  or  to  the  supporting  posts.  In  iron  frame 
houses  it  is  customary  to  hang  overhead 
shafting  from  the  rafters  and  the  shafting 
for  the  side  ventilators  from  the  side  posts, 
using    a    hanger    for    each    rafter    or    post. 


EXTILATIXG 


i;u 


When  the  shafting  is  hung  from  the  sash 
bars  a  hanger  is  attached  to  every  second 
or  third  bar,  usually  to  every  second. 


Fig.  71— 

Open  col- 
umn ventil- 
ator gearing 


Fig.  72.- 
Open       col- 
umn     chain 
operated 
ventilator 
gearing 


Gearing. — Generally  speaking,  there  are 
three  types  of  gearing  utilized  for  operating- 
overhead  ventilator  shafting.  These  are: 
(i)  The  column  gear,  of  which  there  are 
many   different  forms;    (2)    the   chain-oper- 


132 


GREENHOUSES 


ated  gear;  and  (3)  the  rack  and  pinion  gear. 
In  the  column  gear  a  post  or  column  sup- 
ports the  gearing  and  the  wheel  to  which 
the  power  is  applied.  One  form  of  column 
gear  is  known  as  an  open  column 
gear,  because  the  drive  rod  is  not 
inclosed  in  the  column  and  there 
is  no  housing  about  the  gearing. 
In  another  open  column  gear 
type  a  chain  is  used  to  transmit 
the  power.  In  the  closed  col- 
umn types  all  gearing  is  inclosed 
and  runs  in  oil,  much  the  same  as 
in  the  transmission  case  of  an 
automobile.  This  insures  free- 
dom from  noise  and  ease  of 
operation. 

In  the  chain  type  no  columns 
are  recjuired,  a  feature  much 
prized  by  growers.  By  this  sys- 
tem practically  all  the  ventilators 
in  a  house  may  be  operated  from 
one  point,  as  the  chains  may  be 
run  almost  anywhere  in  the  house 
by  the  use  of  pulleys.  The  ab-  ^^or  gearing 
sence  of  columns  means  less  shade. 

The  rack  and  pinion  type  differs  from 
the  two  general  types  mentioned  above,  not 
so  much  in  the  method  of  applying  the  power 


Fig.  n.— 

Closed    col- 
umn  ventil- 


VEXTILATING 


133 


Fig.    74. — Chain    system    of    operating    ventilators.     No 
columns  used 


Fig.  75. — Rack-and-pinion  system  of  operating 
ventilators 


134:  GREENHOUSES 

to  the  shaft  as  in  the  method  of  actually 
opening  the  ventilators.  The  chief  advan- 
tage of  this  system  lies  in  the  fact  that  there 
is  less  torsional  or  twisting  strain  on  the 
shafting  than  when  the  usual  method  is  em- 
ployed, and  they  are  more  powerful.  The 
chief  disadvantage  is  that  provision  must  be 
made  for  giving  the  shaft  several  revolutions, 
while  a  half  or  two-thirds  revolution  is  usual- 
ly sufficient  with  the  more  common  forms. 

Some  practical  growers  claim  that  the  rack 
and  pinion  device  is  very  subject  to  wear  and 
is  a  frequent  cause  of  trouble.  This  is  more 
especially  true  of  the  older  forms  of  this  t3^pe. 
The  fact  that  they  are  not  generally  used 
would  seem  to  indicate  that  practical  growers 
as  a  rule  are  not  yet  convinced  of  their  super- 
iority, though  they  are  now  being  installed  in 
some  large  houses  where  it  is  necessary  to 
operate  long  runs. 

Quite  frequently  the  hand  wheel  and  gear- 
ing are  fastened  to  the  rafters  or  purlin  posts 
and  no  extra  columns  are  required. 

Side  Ventilating  Machinery. — The  essen- 
tial features  of  side  operating  machinery 
are  the  same  as  for  overhead  ventilators. 
When    there    are    side    benches    a    shaft    is 


VENTILATING 


135 


Fig.  76. — Ventilators   (a  and  b)   operated  by  means  of 
rods   with    universal    joints    attached    to    posts    and 
rafters.     No    extra    columns   are    necessary. 

usually  used  and  the  hand  wheel  placed  at  a 
convenient  position  for  the  operator.  When 
there  are  no  benches  along  the  sides  a  com- 
pact device  is  advisable  in  order  to  take  up  as 
little  room  as  possible   (Fig.  78). 


13& 


GREENHOUSES 


Fig.      11. — Device      for 
operating    side  ventilators 


Ventilator    Arms. — 

Ventilator  sash  are 
most  commonly  raised 
and  lowered  by  means 
of  hinged  braces  or 
arms  operated  from 
the  shafting.  There 
are  three  general 
types. 

The  elbow  arm  is 
most  commonly  used 
but  has  the  disadvan- 
tage that  a  long  lever- 
age is  required,  in  order  to  open  the  venti- 
lators to  the  full  width,  which  puts  a  consid- 
erable strain  on  the  shaft. 

The  double  acting  arm  overcomes  this  dif- 
ficulty to  some  extent  as  it  is  possible  to  se- 
cure a  wider  opening  with  a  shorter  leverage, 
but  it  is  necessary  to  rotate  the  shaft 
through  an  extra  half  turn.  On  long  runs 
these  arms  are  now  being  extensively  used  in 
place  of  the  common  elbow  arm. 

The  extending  arm  is  used  in  low  houses, 
or  for  side  ventilators,  or  in  other  places 
where  an  elbow  or  double  acting  arm  would 
extend  into  the  house  so  far  as  to  be  in  the 


VEXTILATING  137 

way.  It  folds  together  when  the  sash  is 
closed  and  occupies  little  space,  but  it  ex- 
tends automatically  when  the  shaft  is  turned. 
It  is  especially  convenient  under  certain  con- 
ditions, but  it  lacks  the  strength  necessary 
for  lono-  runs.         , 


Fig,  78. — Compact  machine  for  operating  side  ventilators 

In  all  systems  the  arms  are  clamped  se- 
curely and  rigidly  to  the  shafting,  and  as 
near  as  possible  to  the  hangers  so  as  not  to 
spring  the  shafting  when  heavily  loaded. 
They  are  spaced  about  3  feet  apart  along  the 
sash.  If  continuous  sash  are  not  used  the 
arms  should  be  distributed  as  follows:  For 
sash  up  to  4  feet  long,  one  arm ;  from  4  to  7 


138 


GREENHOUSES 


Fig.    79. — Types    of    ventilator    arms.     A,    double    acting 
arm;  B,  elbo-w  arm;  C,  extending  arm  closed;  D,  extend- 
ing  arm   open 


VENTILATING  139 

feet  long,  two  arms;  and  from  8  to  ii  feet 
long,  three  arms,  etc. 

Capacity  of  Ventilating  Apparatus. — The 

capacity  of  ventilating  apparatus  depends 
largely  upon  the  size  and  method  of  manu- 
facture, but  the  length  of  run  is  limited  to 
the  torsional  strength  of  the  shafting.  In 
long  lengths  there  is  always  more  or  less  tor- 
sion, so  that  the  ventilators  at  the  extreme 
end  do  not  open  as  wide  as  those  close  to 
where  the  power  is  applied.  This  is  of  little 
consequence  in  summer  when  the  ventilators 
are  wide  open,  but  in  winter,  when  only 
slight  ventilation  is  required,  it  may  result  in 
the  sash  at  the  end  of  the  shaft  not  open- 
ing at  all  and  the  ventilation  will  thus  be  un- 
even and  unsatisfactory.  Moreover,  the  sash 
are  likely  to  be  frozen  down  in  winter  and 
the  tendency  for  the  shafting  to  twist  is  thus 
increased.  It  is  wise  to  have  a  wide  margin 
for  safety. 

An  indication  of  the  length  of  shafting 
that  may  be  used  with  safety  is  given  on 
page  130.  Tests  show  that  one  and  a 
fourth-inch  standard  pipe  has  a  torsional 
strength  42   per   cent,   greater   than    i-inch 


.140  GREENHOUSES 

double-strength  pipe  and  that  the  weights 
are  practically  the  same.  The  price  of  i- 
inch  double-strength  pipe  averages  about  25 
per  cent  more  than  standard  one  and  a  fourth 
inch  pipe.  It  is  evident,  therefore,  that  for 
long  runs  it  is  not  only  safer  but  more 
economical  to  use  one  and  a  fourth-inch 
standard  pipe  than  i-inch  double-strength. 

Generally  speaking,  a  150-foot  run  is  about 
the  limit  when  elbow  arms  are  used.  This 
may  be  slightly  increased  b}^  using  the 
double  acting  arms,  and  still  further  by  us- 
ing the  rack  and  pinion  system.  This  is 
equivalent  to  saying  that  the  ventilators  in  a 
house  300  or  350  feet  long  may  be  operated 
from  one  station  by  having  machines  located 
in  the  center  of  the  house  and  operating  each 
way.  It  is  economy  to  have  all  ventilator 
sash  for  one  house  operated  from  the  same 
station  if  possible. 

Sliding  Shaft  System. — In  order  to  enable 
the  operator  to  care  for  an  extremely  long 
line  of  sash  from  one  station  a  sliding  shaft 
system  has  been  devised.  In  this  case  the 
shafting  is  solid  and  square,  and  instead  of 
rotating  it  slides  backward  and  forward,  the 
motion  being  given  by  a  pinion  working  on 
a  screw  or  worm  gear  at  one  end  of  the  shaft- 


VEXTILATIXXx 


141 


I!"    I 


Fig.  80. — Sliding  shaft  system  for  opcrati::g  ventilators 

This  sliding  moveinerit  is  utilized  to 
operate  the  sash  hy  means  of  a  right  angle 
lever,  pivoted  at  the  angle  with  the  short  arm 
attached  to  the  shaft  and  the  long  arm  to  the 
sash.  It  is  claimed  for  this  system  that  it 
will  operate  a  line  of  sash  500  feet  long. 


CHAPTER  IX 
BEDS,  BENCHES  AND  WALKS 

In  the  earlier  greenhouses,  plants  were  al- 
most always  grown  on  raised  benches.  This 
was  partly  for  the  convenience  of  the  grow- 
er and  partly  because  the  houses  were  almost 
always  erected  with  high,  solid  side  walls 
and  it  was  necessary,  in  order  to  secure  satis- 
factory growth,  to  bring  the  plants  close  to 
the  glass  roof.  In  modern  houses,  when  all 
or  part  of  the  side  walls  are  of  glass,  raised 
benches  are  not  so  necessary,  and  are  very 
commonly  dispensed  with  and  the  plants 
grown  directly  in  the  soil  which  forms  the 
floor.  This  is  particularly  true  when  vege- 
tables such  as  lettuce,  tomatoes  or  cucum- 
bers are  grown. 

Florists,  as  a  rule,  have  been  loth  to  give 
up  the  use  of  benches  and  present  the  follow- 
ing arguments  in  their  favor,  (i)  It  is 
more  convenient  to  care  for  plants  when 
grown  on  raised  benches  than  when  grown 
on  the  ground.      (2)  Benches  make  possible 

142 


BEDS.  BENCHES  AXD  WALKS  143 


■^ 


144  GREENHOUSES 

the  placing  of  the  heating*  pipes  underneath, 
which  makes  them  less  conspicious  and  at : 
the  same  time  affords  a  method  of  giving  , 
''bottom  heat,"  which  is  considered  advant- 
ageous with  many  plants.  (3)  It  is  main- 
tained that  there  is  a  better  circulation  of 
air  about  plants  grown  on  benches  and  that 
the  plants  are  less  subject  to  disease.  (4) 
The  temperature  and  moisture  of  the  soil 
can  be  more  easily  regulated  in  benches. 
(5)  Low-growing  plants  make  a  better  dis- 
play when  grown  on  benches. 

The  following  are  the  most  common  dis- 
advantages claimed  by  those  who  urge 
against  the  use  of  benches,  (i)  They  are 
expensive  to  build  and  maintain.  (2)  They 
do  not  admit  of  an  economical  use  of  space. 
(3)  The  soil  dries  out  rapidly.  (4)  The  soil 
has  to  be  changed  more  often.  (5)  It  is 
more  difficult  to  use  labor-saving  tools  such 
as  wheel-barrows.  (6)  All  work  must  be 
done  by  hand.  In  large  houses  it  is  possible, 
when  plants  are  grown  on  the  ground,  to  pre- 
pare the  soil  with  a  horse  or  with  wheel  hoes. 
(7)  With  high-growing  plants  such  as  to- 
matoes and  cucumbers,  it  is  difficult  to  har- 
vest the  crop  when  they  are  grown  on  high 
benches. 


BEDS,  ?»KNCHES  AXD  WAEKS  145 


Fig.  82. — Tomatoes  growing  in  solid  raised  beds 


Fig.  S3. — Solid  raised  beds  of  hollow  building  tile  in  use 
at  the   jNlichigan  Agricultural   College 


146  GREENHOUSES 

Raised  Beds. — To  overcome  some  of  the 
objections  to  raised  benches,  many  growers 
use  solid  raised  beds,  the  height  varying  from 
a  few  inches  to  that  common  for  benches. 
Such  beds  dry  out  less  quickly  than  do 
benches,  the  soil  does  not  have  to  be  removed 
as  frequently,  and  they  are  less  expensive  to 
maintain.  They  are  open  to  some  of  the  ob- 
jections urged  against  benches  and  do  not 
possess  many  of  the  advantages  afforded  by 
culture  in  the  open  soil.  The  width  and  ar- 
rangement follows  closely  that  of  benches. 

Raised  Benches. — Benches  are  exposed 
continuously  to  conditions  which  favor  their 
rapid  deterioration.  Unless  well  constructed 
of  good  material,  they  are  a  source  of  con- 
stant annoyance.  Many  growers  use  wooden 
benches.  Others  use  benches  having  iron 
frames,  and  sides  and  bottoms  of  wood,  tile, 
slate  or  cement  slabs.  Still  others  use  solid 
concrete  benches.  All  forms  have  their  ad- 
vantages and  their  advocates. 

Wood  Benches. — Wood  benches  have  the 
advantage  of  slightly  less  first  cost,  though 
if  good  material  is  used,  the  cost  will  be  near- 
ly as  great  as  for  iron  frame  benches.  In 
permanent   houses   nothing   but   cypress    or 


BEDS,  BENCHES  AND  WALKS 


U^ 


cedar  should  be  used,  genuine  pecky  cypress 
being  undoubtedly  the  best.  The  sides 
and  bottom  boards  are  not  less  than  i  inch 
thick.     The  side  boards  are  8  inches  wide. 


i\\ni\t 


\IIIU\iff^riiM  ^11- 


3       I 


^r^y 


B 

Fig.  84. — Two  types  of  wood  benches.  A,  bottom  boards 
running  lengthwise;   B,  bottom  boards   running  crosswise 

The  width  of  the  bottom  boards  is  imma- 
terial, except  that  when  in  place  they  have  a 
space  of  a  fourth-inch  between  them  for 
drainage.  They  are  usually  run  length- 
wise of  the  bed  and  are  supported  by  cross- 
beams, spaced  not  more  than  4  feet  apart. 

The  size  of  the  cross  beams  will  depend 
somewhat  on  the  width  of  the  bench,  as 
follows : 

For  benches  up  to  4  feet  wide 2x4  inches 


For  benches  from  4  to  6  feet  wide 
For  benches   over  6  feet   wide 


c6  inches 


. . . .2x8  inches 

The  legs  or  posts  are  at  least  4x4  inches 
in  size,  and  rest  on  concrete  or  brick  piers. 
Sometimes,  when  cement  walks  are  used, 
they  are  made  to  extend  under  the  benches 
far  enough  to  act  as  a  foundation  for  the 
posts. 


US  GREENHOUSES 

To  guard  against  warping  of  the  side  and 
d   boards    of   wood    benches,    angle    irons 

Qay  be  used  in  the  corners  and  along  the 

gdes,  and  fastened  by  screws  or  small  bolts. 

ick    piers    may   be   used    in    place    of    the 

ooden  legs.       The  wooden  legs,  however, 

will  usually  outlast  the  bottom  boards  and 

cross-beams. 


Fig.  85. — A  type  of  iron  frame  bench 

Iron  Frame  Benches. — In  the  majority  of 
iron  frame  benches,  i-inch  wrought-iron 
pipe  is  used.  It  is  rarely  threaded  but  is  tied 
together  with  split  malleable  iron  castings 
by  the  use  of  bolts  and  set  screws.  The 
sides  and  bottom  may  b^  made  of  wood,  iron, 
slate,  tile  or  even  of  cement  slabs.    All  are 


BEDS,  BENCHES  AND  WALKS  I  il) 

removable  and  may  be  replaced  without  tak- 
ing down  the  frame.  ■-   ' 

Iron  frame  benches  with  cypress  sides  and 
bottoms  are  now  much  in  favor.  They  are 
but  little  more  expensive  than  the  all-wood 
benches  and  are  in  most  cases  more  satis- 
factory, as  the  frames  are  nearly  indestruct- 
ible. They  should,  however,  be  made  of 
wrought-iron  pipe  rather  than  of  steel. 
They  may  be  had  in  two  forms,  one  in  which 
the  bottom  boards  run  lengthwise  of  the 
bench  and  another  in  which  they  run  cross- 
wise. The  advantage  of  the  latter  is  that 
short  lengths  may  be  used.  These  benches 
may  be  purchased  with  all  parts  cut  to  order, 
or  they  may  be  easily  cut  by  anyone  familiar 
with  pipe  cutting. 

Iron  frame  benches  are  also  made  of  angle 
iron  or  structural  iron  of  different  forms. 
The  chief  disadvantage  of  these  is  that  the 
iron  cannot  be  worked  readily  by  the  ordin- 
ary workman  and  must  be  cut  and  fitted  at 
the  factory. 

Concrete  Benches. — Concrete,  because  of 
its  permanency,  is  often  recommended  for 
greenhouse  benches,  and  its  use  is  increas- 
ing".     In  general,   there  are   two   separcite 


150 


GREENHOUSES 


BEDS,  BENCHES  AND  WALKS  151 

types.  In  one  type  the  legs,  bottom  and 
sides  are  cast  separately  in  molds  and  then 
put  together  in  the  greenhouse.  In  the  other 
type  the  whole  bench  is  cast  in  a  form  built 
in  the  house  where  it  is  to  stand.  There 
are  at  least  two  firms  having  patents  on 
cement  greenhouse  benches  and  who  are  pre- 
pared to  sell  or  rent  molds  or  forms  for  mak- 
ing them.  It  is  also  possible  for  a  skilled 
mechanic  to  make  forms  to  suit  any  special 
location  or  for  any  form  of  bench.  In  mak- 
ing concrete  benches,  care  should  be  taken 
to  provide  for  adequate  drainage  through  the 
bottom  and  to  see  that  they  are  thoroughly 
reinforced. 

There  has  been  some  discussion  as  to  the 
effect  of  concrete  benches  on  the  growth  of 
plants.  The  author  has  had  but  little  prac- 
tical experience  with  them  but  quotes  from 
one  of  the  largest  users  of  concrete  benches 
in  the  country,  as  follows : 

''At  my  place  I  use  only  concrete  benches 
and  the  results  and  advantages  .have  been 
very  satisfactory,  but  I  want  to  be  open  and 
frank  concerning  the  disadvantage,  which  is 
only  for  the  first  year.  Something  in  the 
line  of  a  chemical  of  a  whitish  nature  ap- 
pears on  fresh  new  cement,  and  that  seems 


152  GREENHOUSES 

to  be  injurious  to  plants;  but  after  you  have 
filled  the  benches  with  soil  and  used  them 
the  first  year,  the  soil  generally  eats  or  ab- 
sorbs this  chemical,  and  the  roots  of  carna- 
tion plants  or  anythmg  else  cling  to  the  ce- 
ment slabs  the  same  as  they  do  to  slate.  A 
good  remedy  to  get  rid  of  this  so  that  it  will 
not  injure  the  plants  is  simply  to  put  air- 
slaked  lime  or  rather  heavy  whitewash  on 
the  inside  of  the  bench,  and  that  seems  to 
protect  the  plants  from  coming  in  contact 
with  the  chemical  mentioned." 

Height    and    Width    of    Benches. — The 

height  of  greenhouse  benches  is  largely  de- 
termined by  that  most  convenient  for 
the  operator  to  work.  This  in  turn  depends 
upon  the  nature  of  the  plants  to  be  grown. 
For  example,  when  low-growing  plants  like 
lettuce  are  grown,  a  bench  32  inches  high  is 
about  right ;  but  when  carnations  are  grown 
this  may  be  so  high  as  to  make  disbudding 
difficult.  This  refers  to  the  distance  from 
the  top  of  the  walk  to  the  top  of  the  sides 
of  the  bench. 

The  width  of  the  bench  depends  on  the 
width  of  the  house,  on  the  arrangement  of 
the  benches,  and  to  some  e:?^tent  on  the  kind 


BEDS,  BENCHES  AND  WALKS 


153 


of  plants  to  be  grown.  It  is  limited  to  the 
distance  a  man  can  conveniently  reach  in 
caring  for  the  plants.  This  distance  is 
about  2>^  feet  or  rarely  3  feet.  In  other 
words,  benches  that  can  be  worked  from 
one  side  only  should  be  no  more  than  2V2  or 
3  feet  wide,  and  benches  which  may  be 
worked  from  both  sides  should  be  no  more 


Fig.  87. — Method  of  arranging  benches  in  an  uneven- 
span   house   to    secure   best   advantage   of   the    sunlight 

than  5>^  or  rarely  6  feet  wide.  In  uneven 
span  houses  it  is  sometimes  advisable  to  ele- 
vate the  walks  and  benches. 

Arrangement  of  Benches. — This  is  gov- 
erned by  the  width  of  the  house,  the  use  for 
which  the  house  is  designed,  the  height  of 
the  beds  or  benches  and  by  the  individual 
preference  of  the  owner.    Commercial  grow- 


154 


GREENHOUSES 


ers  look  upon  walks  as  waste  space  and  en- 
deavor to  keep  them  as  narrow  as  is  con- 
sistent with  ease  and  economy  in  getting 
about  the  houses.  In  private  houses,  con- 
servatories and  show  houses,  the  walks  are 
sufficiently  wide  to  allow  two  persons  to  pass 
easily. 


30- 


5- 


Fig.  88. — An  arrangement  of  benches  in  a  30-foot  house. 
Only  66  2-3  per  cent  of  the  floor  space 
available  for  crops 

In  figures  88  and  89  are  illustrated  two 
methods  of  arranging  benches  in  a  30-foot 
house.  By  the  first  method  four  benches, 
each  five  feet  wide,  are  provided  and  661  per 
cent  of  the  floor  space  is  available.  By  the 
second  method  three  wide  and  two  narrow 
benches  are  provided  and  7Si  per  cent  of  the 
floor  space  is  available.    In  the  latter  method 


BEDS,  BENCHES  AND  WAEKS 


155 


the  side  l3enches  extend  the  entire  length  of 
the  house  and  one  walk  is  eliminated. 

It  is  worth  while  to  exercise  considerahle 
care  in  determining  the  arrangement  of 
the  benches,  especially  in  commercial  houses. 
As  a  rule  a  walk  along  the  side  of  a  house 
is  an  extravagance.     When  the  width  of  the 


1/.' 

^ 

—          UU 

-ai- 

-5.- 

-i^'-S"- 

Fig.  89. — Another  arrangement  of  benches  in  a  30-foot 

house.     By  this  arrangement  72)  1-3  per  cent  of  the  floor 

space  is  available  for  growing  crops 


house  admits,  it  is  usually  more  economical 
to  have  narrow  benches  along  each  side. 

When  low  beds  are  used,  the  walks  may 
be  narrower  than  with  high  benches  as  peo- 
ple can  pass  more  readily.  In  conserva- 
tories and  show  houses  3  feet  is  none  too 


156  GREENHOUSES 

wide.  In  commercial  houses  with  high 
benches,  from  20  to  24  inches  is  a  common 
width.  When  low  beds  are  used,  the  walks 
are  sometimes  as  narrow  as  14  or  16  inches. 
It  is  often  advisable  to  arrange  the 
benches  so  as  to  have  the  center  walk  of  ex- 
tra width,  which  will  allow  of  the  use  of 
a  wheel  barrow  or  cart  in  removing  and  re- 
plenishing the  soil  and  for  other  purposes. 

Material  for  Walks. — Concrete  is  unques- 
tionably the  best  material  for  walks.  Water 
has  no  effect  on  it;  it  is  substantial;  it  may 
be  used  as  a  foundation  on  which  bench  legs 
and  ventilator  columns  may  stand;  and  it 
may  be  quickly  and  easily  laid.  In  conserv- 
atories and  private  houses  nothing  can  take 
its  place.  For  data  on  concrete  construction 
see  Chapter  XIV. 

In  commercial  houses  coal  ashes  are  often 
used.  Ashes  must  be  kept  away  from  the 
pipes  as  the  sulphur  they  contain  will  cause 
the  pipes  to  corrode  very  rapidly. 

Curbs. — For  convenience  and  cleanliness, 
many  growers  who  plant  directly  on  the 
ground  prefer  to  have  their  houses  marked 
oft*  into  regular  beds,  divided  by  narrow 
walks  and  surrounded  by  a  curb  to  keep  the 


BEDS,  BENCHES  AND  WALKS  157 

,soil  in  place.  In  time,  the  constant  addition 
of  manure  raises  the  soil  in  these  beds  so 
that  they  become  in  reality  raised  beds. 
Board  or  plank  curbs  are  rarely  satisfactory, 
as  the  moisture  of  the  soil  on  one  side  causes 
them  to  warp.  The  most  satisfactory  and 
economical  curbs  are  made  of  concrete, 
which  is  heavily  reinforced  with  iron  rods 
when  it  is  poured. 


CHAPTER  X 

GREENHOUSE  HEATING 

Generally  speaking,  there  are  only  two 
satisfactory  methods  of  greenhouse  heating: 
Steam  and  hot  water.  Direct  heating  by 
stoves  is  not  satisfactory  even  in  small 
houses,  and  no  satisfactory  system  has  yet 
been  devised  for  the  use  of  hot-air  furnaces. 
The  only  method  aside  from  steam  or  hot 
water  which  deserves  mention  is  heating  by 
flues.  They  are  wasteful  of  fuel,  and  their 
use  is  not  justified,  except  in  cheaply  con- 
structed houses  which  are  used  only  for  a 
few  months  in  the  spring  or  fall. 

The  principles  pertaining  to  greenhouse 
heating  are  much  the  same  as  those  involved 
in  heating  other  buildings,  except  that  the 
loss  of  heat  is  greater  from  glass  than  from 
wood  or  brick  walls,  and  a  higher  and  more 
constant  night  temperature  is  required  than 
is  necessary  in  dwellings.  For  this  reason, 
relatively  more  radiating  surface  is  required 
and  boilers  of  larger  capacity  are  needed. 

158 


GREENHOUSE  HEATING  159 

Heating  with  Flues. — In  heating  with 
flues  the  equipment  consists  simply  of  a 
furnace  at  one  end  of  the  house  and  a  chim- 
ney at  the  other,  the  two  being  connected  by 
a  flue,  carried  underneath  the  bench  or 
buried  just  underneath  the  soil,  through 
which  the  heat  and  smoke  are  carried.  This 
may  be  made  of  brick,  but  large-size  drain 
or  sewer  tile  are  more  commonly  used.  These 
withstand  the  heat  and  are  easily  and  cheap- 
ly put  in  place.  It  is  best  to  have  the  flue 
slope  upward  slightly  toward  the  chimney. 
As  has  already  been  stated,  this  method  is 
wasteful  of  fuel.  It  is  also  difficult  to  regu- 
late. It  is  still  employed  to  some  extent 
by  vegetable  gardeners  in  cheap  houses, 
used  only  in  late  winter  or  early  spring  for 
the  starting  of  early  vegetable  plants,  sweet 
potatoes,  etc. 

Hot  Water  vs.  Steam. — There  has  been 
much  discussion  as  to  the  relative  virtues  of 
hot  water  and  steam  for  use  in  greenhouse 
heating.  It  may  be  well  to  consider  here 
some  of  the  advantages  claimed  for  each. 
For  hot  water  the  following  are  claimed: 
(i)  It  provides  a  more  even  heat  than  steam. 
(2)  The  radiating  pipes  are  not  so  hot,  and 


160  GREENHOUSES 

plants  near  them  are  less  likely  to  be  injured 
than  when  steam  is  used.  (3)  It  requires 
less  frequent  firing,  since  warm  water  is  al- 
ways circulating  in  the  pipes  as  long  as  there 
is  any  fire  in  the  furnace,  whereas,  with 
steam  it  is  necessary  to  keep  the  water  boil- 
ing to  keep  steam  in  the  pipes.  (4)  For  the 
above  reason  a  night  fireman  is  not  required 
in  small  houses  equipped  with  hot  water.  (5) 
It  is  less  dangerous.  This  is  more  apparent 
than  real,  for  steam  is  usually  carried  at  low 
pressure.  (6)  It  is  claimed  that  hot  water 
requires  less  fuel.  Theoretically  this  should 
be  true,  but  in  practice  it  has  not  been  very 
definitely  proven.  (7)  Water  will  hold  heat 
for  some  time  if  the  fire  should  accidentally 
go  out. 

The  following  advantages  are  claimed  for 
steam:  (i)  Less  cost  of  installation.  (2) 
Steam  requires  fewer  radiating  pipes  hence 
less  shade  is  cast  when  the  pipes  are  placed 
overhead  than  when  hot  water  is  used.  (3) 
Less  time  is  required  to  get  up  heat,  as  there 
is  a  relatively  small  body  of  water.  (4)  A 
greater  area  may  be  warmed  from  a  given 
heating  plant  than  with  hot  water,  for  the 
steam  may  be  forced  farther.     (5)  A  steam 


GREENHOUSE   HEATIXCx  IGl 

plant  may  be  used  to  furnish  steam  for  soil 
sterilization. 

All  the  above  apply  more  especially  to 
small  ranges  than  to  large  ranges.  As  a 
rule,  hot  water  is  more  o'enerallv  used  in 
ranges  covering  up  to  20,000  square  feet  and 
steam  in  larger  ranges,  although  there  are 
many  exceptions.  At  present  the  tend- 
ency seems  to  be  toward  the  use  of  hot  water 
rather  than  steam. 

In  an  investigation  recently  made  by  the 
author  among  a  large  number  of  greenhouse 
owners,  86  per  cent,  of  those  having  20,000 
sc[uare  feet  or  more  under  glass  preferred 
steam  heat.  The  chief  reasons  stated  were, 
''better  control,"  ''cheaper  maintenance,"  and 
"less  shade  from  pipes."  Six  per  cent,  pre- 
ferred a  combination  of  hot  water  and  steam. 
The  remaining  8  per  cent,  preferred  hot 
water,  stating  as  their  reasons,  "steadier 
heat,"  "plants  grow  better,"  "pipes  do  not 
rust  out  during  the  summer  as  with  steam," 
and  "cheaper  to  operate  in  spring  and  fall 
when  little  heat  is  required." 

Of  those  having  less  than  20,000  square 
feet  under  glass,  74  per  cent,  preferred  hot 
water,    giving    in    addition    to    the    reasons 


162 


GREENHOUSES 


GREENHOUSE  HEATING  163 

named  above,  ''less  labor  to  lire,  especially  at 
night"  and  '"needs  no  night  fireman." 

Combination  Systems. — A  combination  of 
hot  water  and  steam  may  often  be  used  to 
advantage.  B}^  this  means  steam  may  be 
had  for  power  and  at  the  same  time  be  util- 
ized for  heating.  In  cold  weather  both  boil- 
ers may  be  used  for  heating,  while  in  mild 
weather  the  steam  boiler  alone  may  be  used, 
thus  furnishing  the  necessary  heat  and 
power. 

Another  and  more  simple  combination  of 
hot  water  and  steam  heating  which,  how- 
ever, is  more  expensive  in  installation,  con- 
sists of  two  separate  sets  of  heating  coils, 
one  of  which  is  connected  with  a  steam  boil- 
er and  the  other  with  a  hot  w^ater  boiler.  The 
steam  is  used  when  a  small  amount  of  heat 
is  needed  quickly  on  cold  nights  in  early  fall 
or  late  spring,  and  to  supplement  the  hot 
water  in  severe  winter  weather. 

In  any  system  of  heating  it  is  much  safer, 
as  well  as  more  economical  in  operation,  to 
install  two  or  more  boilers  rather  than  to 
depend  on  one  large  one.  Both  may  be 
used  in  severe  weather  and  in  case  of  acci- 
dent to  one,  the  other  may  be  forced  for  a 


164  GREENHOUSES 

few  days  and  thus  protect  the  plants  from 
injury  by  freezing,  which  would  inevitably 
result  if  only  one  boiler  was  in  use. 

Heating  Coils. — Because  of  the  large 
amount  of  heating  surface  required,  and  be- 
cause all  parts  of  a  greenhouse  must  be  kept 
at  as  nearly  uniform  temperature  as  possible, 
radiators  such  as  are  used  in  private  houses 
have  not  been  found  practicable  in  green- 
house heating.  Instead,  long  coils  of 
wrought  iron  or  steel  pipe  are  used.  For 
steam  heating  these  coils  are  commonly  of 
I  or  I /4-inch  pipe.  In  hot  water  heating  they 
are  slightly  larger,  varying  from  i/4  to  2 
inches.  In  the  early  days  of  hot  water  heat- 
ing large  cast-iron  pipe,  often  as  large  as 
four  or  five  inches  in  diameter  was  used.  It 
is  still  used  to  some  extent,  but  more  often 
in  small  private  conservatories  than  in  com- 
mercial houses. 

There  is  very  little  to  be  said  in  favor  of 
using  cast-iron  pipes.  The  fact  that  they  are 
now  so  little  used  shows  that  they  have  no 
special  merit.  The  smaller,  wrought  pipe  is 
lighter  and  much  more  easily  handled;  is 
screwed  together  instead  of  caulked  with 
lead  and  oakum;  has  much  more  radiating 


GREENHOUSE  HEATING 


165 


surface  in  proportion  to  the  volume  of  water 
contained;  can  be  placed  along  the  side 
walls  or  hung  on  the  supporting  posts  in- 


Fig.    91. — Under-bench    heating    with    large    cast-irun 
pipes 

stead  of  having  to  be  supported  on  mason- 
ry piers ;  and  permits  of  a  more  perfect  con- 
trol of  the  heat. 


166  GREENHOUSES 

Heating  coils  are  made  by  joining  several 
pipes  together  by  means  of  headers.  The 
hot  water  is  conducted  to  the  coils  from  the 
boiler  by  means  of  a  larger  pipe  known  as 
a  flow  pipe  or  feed  pipe.  It  is  returned  to 
the  boiler  by  means  of  a  return  pipe.  In 
steam  heating  the  coils  are  often  so  arranged 
that  the  water  formed  from  the  condensed 
steam  returns  to  the  boiler  through  the  flow 
or  feed  pipe,  instead  of  through  a  separate 
return  pipe. 


CHAPTER  XI 

HOT  WATER  INSTALLATION 

General  Principles. — Before  discussing 
the  installation  of  a  hot  water  heating  sys- 
tem it  is  necessary  to  have  in  mind  the  phy- 
sical and  mechanical  principles  involved. 
Briefly  they  are  these:  Water  increases  in 
volume  as  it  is  heated  and  it  is  consequently 
lighter  in  weight.  When  a  fire  is  lighted  un- 
der a  water  boiler  the  water  around  the  heat- 
ing surface  expands  and,  being  lighter,  is 
forced  upward  by  the  heavier,  colder  water. 
Popularly  speaking,   the  hot  water  'Vises." 

The  practical  problem  is  to  conduct  the 
hot  w^ater  from  the  boiler  to  the  coils  where 
the  large  radiating  surface  permits  the  water 
to  give  up  its  heat  to  the  air  in  the  house 
and  then,  as  it  becomes  colder  and  heavier, 
to  conduct  it  back  to  the  boiler  where  it  will 
displace  the  warmer  and  lighter  w^ater  there. 
Gravity  is  the  force  utilized  to  produce  cir- 
culation. It  acts  with  a  force  proportional 
to  the  difTerence  in  w^eight  between  the  col- 
umn of  warm  water  and  the  column  of  cool 
water. 

167 


168 


GREENHOUSES 


The  following  table  shows  the  weight  of  a 
cubic  foot  of  distilled  water  at  different 
temperatures. 


32  degrees  F., 62.42  pounds 

100  "  ....62.02 

110  "  ....61.89 

120  ''  ....61.74 

130  "  ....61.56 

140  "  ....61.37 

150  "  ....61.18 

160  "  ....60.98 


170  degrees  F.. 60.77  pounds 

180  "  ..60.55 

190  "  ..60.32 

200  "  ..60.07 

210  "  ..59.82 

220  -  ..59.76   " 

230  ''  ..59.37 


From  the  above  table  it  is  apparent  that  a 
cubic  foot  of  water  entering  the  boiler  at  140 
degrees  is  0.82  pounds  heavier  than  an  equal 
quantity  leaving  the  boiler  at  180  degrees. 
It  is  evident  that  the  higher  the  columns  of 
water  the  greater  will  be  the  difference  in 
weight,  and  consequently  the  more  rapid  will 
be  the  flow. 

The  various  factors  influencing  the  veloc- 
ity of  water  in  a  gravity  hot  water  system 
are  embodied  in  the  following:  formula. 


v^: 


2gh  (w— W) 
(w+W) 

In  this  formula,  V=the  velocity  in  feet  per 
second,  g=the  force  of  gravity  (32.16),  h= 
the  total  height  of  the  system,  W=the  weight 
of  a  cubic  foot  of  water  wl^en  it  leaves  the 


HOT  WATER  INSTALLATION  169 

boiler  and  w=the  weight  of  a  cubic  foot  of 
water  when  it  enters  the  boiler. 

This,  of  course,  disregards  friction.  The 
practical  application  is  that  when  it  is  de- 
sired to  increase  the  velocity  of  the  water; 
e.g.  in  long  runs,  it  may  be  done  by  either 
lowering  the  boiler  or  by  raising  the  height 
of  the  flow  pipes. 

The  following  table  shows  the  velocity  in 
feet  per  second  in  a  hot  water  system  under 
various  conditions. 

Difference   in  temperature  on  leaving  and 
entering    boiler 
10°  15°         20°        30°  40° 

F'eet  Per  second 
0.750        0.922      1.09 
1.06  1.32         1.55 

1.50  1.85        2.19 

1.83  2.26        2.68 

Arrangement  of  Piping. — There  are  two 
approved  methods  of  arranging  the  piping 
for  hot-water  heating.  One  is  known  as  the 
''down  hill" ;  the  other  as  the  ''up  hill."  In  the 
former  the  highest  point  in  the  system  is 
directly  above  the  boiler.  In  the  latter  the 
highest  point  is  at  the  end  of  the  system 
farthest  from  the  boiler.  Either  is  satisfac- 
tory and  is  preferred  to  the  "level"  system 
sometimes  advocated.   In  either  the  "down 


Height 

Difi 

of 

Column 

5° 

5  ft. 

0.541 

10   '' 

0.765 

20   " 

1.085 

30   " 

1.35 

1.33 

1.51 

1.88 

2.04 

2.66 

3.01 

3.26 

3.71 

170 


GREENHOUSES 


hill"  or  the  "up  hill"  system  the  air  which 
collects  in  the  pipes  will  eventually  reach  the 
highest  point  when  it  may  be  allowed  to 
escape  through  an  automatic  air  valve.  In 
the  ''level"  system  slight  sags  and  raises  are 
likely  to  occur  and  the  air  will  collect  in  the 
higher  parts  and  cause  trouble. 


. 

^ 

B 

-=t. 

c 

^ ? 

-1 s 

f D                                     ^-^ 

J 

^ 

£ 

A 

L].. 

^ 

Fig.  92. — Diagram  showing  "down-hill"  and  "up- 
hill" systems  of  piping.  A,  boiler;  B,  flow  pipe; 
C,  C,  headers;  D,  radiating  pipes  or  coils;  E,  re- 
turn pipe;  F,  automatic  air  valve;  x  indicates 
height   of  water   column 

The  author  prefers  the  "down  hill"  system 
when  the  flow  pipes  are  carried  in  the  upper 
part  of  the  house  and  the  coils  are  consider- 
ably lower.  When  all  the  pipes  must  be  in 
the  lower  part  of  the  house,  or  under  the 
benches,  he  prefers  the  "up  hill"  system.  The 


HOT  WATER  INSTALLATION         171 


majority  of  greenhouse  oper- 
ators seem  to  be  in  accord 
with  this  view.  Practically 
speaking  there  appears  to  be 
but  little  difference  in  the 
efficiency  of  the  two  systems 
and  the  convenience  and  the 
arrangement  of  the  house  de- 
termines the  choice  to  a  con- 
siderable extent. 

Estimating     Radiation.  — 

The  calculations    for   green-   S^automa1ic''i'i: 
house  heating  are    based    on  valve 

certain  fundamental  facts  which  for  hot 
water  may  be  stated  briefly  as  follows:  A 
square  foot  of  glass  will  give  off,  under  or- 
dinary greenhouse  conditions  in  winter 
weather,  approximately  i  B.  T.  U-*  of  heat 
per  hour,  for  each  degree  difference  in  tem- 
perature between  the  air  inside  the  green- 
house and  that  outside.  A  good  wood,  brick 
or  concrete  wall  will  give  off  about  a  sixth 
as  much,  or  a  sixth  B.  T.  U.  per  square  foot 
per  hour.  It  is  customary  to  divide  the  total 
wall  surface  by  six  and  consider  it  as  equiva- 
lent to  glass. 

*British  Thermal  Unit;  the  amount  of  heat  required  to 
raise  one  pound  of  distilled  water  from  62  to  63 
degrees  F. 


172  GREENHOUSES 

To  arrive  at  an  estimate  of  the  possible 
heat  loss  from  a  greenhouse  add  to  the  total 
square  feet  of  exposed  glass  surface  a  sixth 
of  the  total  square  feet  of  exposed  wall  sur- 
face, and  multiply  the  sum  by  the  difference 
between  the  temperature  at  which  the  house 
is  to  be  kept  and  the  lowest  outside  tem- 
perature which  will  probably  be  experienced. 
Suppose,  for  example,  that  a  house  has 
TO,ooo  square  feet  of  glass  and  equivalent 
glass,  that  it  is  desired  to  keep  it  at  a  night 
temperature  of  50  degrees,  and  that  the  low- 
est outside  night  temperature  to  be  expected 
is  — 10  degrees.  The  number  of  B.  T.  U. 
given  off  by  such  a  house  under  these  con- 
ditions would  be  [50° —  (—10°)]  X  I  x  10  x 
10,000  or  600,000  B.  T.  U.,  and  enough  heat- 
ing coils  must  be  provided  to  supply  this 
amount. 

In  hot  water  heating  the  coils  will  give 
off  approximately  two  B.  T.  U.  per  square 
foot  of  surface  per  hour  for  every  degree 
difference  in  temperature  between  that  of 
the  coil  and  that  of  the  surrounding  air.  The 
average  temperature  of  the  coils  may  be 
taken  to  be  160  degrees,  and  if  the  house  is 
to  be  maintained  at  50  degrees  the  difference 
will  be  no  degrees.     Multiplying  no  by  2 


HOT  WATER  INSTALLATION  173 

we  have  220  or  the  numher  of  B.  T.  U.  o-iven 
off  by  each  square  foot  of  radiating  surface 
per  hour.  If,  then,  we  divide  600,000  by 
220  we  have  2,y2y  which  is  the  numl)er  of 
square  feet  of  radiating-  surface  to  be  pro- 
vided. 

These  principles  may  be  embodied  in  the 
following  formula  where  R=  the  amount  of 
radiating  surface  required  in  square  feet;  T^ 
the  temperature  to  be  maintained  inside  the 
house;  t,  the  lowest  outside  temperature  to 
be  expected;  and  G,  the  number  of  square 
feet  of  glass  and  equivalent  glass. 

(T-t)  X  G 
~(160-Tj  2 

This  formula  gives  a  wide  margin  of  safe- 
ty. Most  builders  prefer  to  use  consider- 
ably less  radiating  surface  and  depend  on 
forcing  the  furnace  in  extremely  cold 
weather.  By  so  doing  the  temperature  of 
the  coils  may  be  kept  at  180  degrees  or  even 
considerably  higher  under  favorable  condi- 
tions and  the  amount  of  radiation  required 
will  be  correspondingly  less. 

Amount  of  Pipe  Required. — Having  esti- 
mated the  amount  of  radiation  required  the 
next  problem  is  to  find  the  quantity  of  pipe 


m 


GREENHOUSES 


necessary  to  provide  this  amount.  For  ex- 
ample, I  linear  foot  of  i/^-inch  pipe  furnishes 
about  half  a  square  foot  of  radiating  surface. 
Divide  the  number  of  square  feet  of  radia- 
tion required  by  the  outside  area  of  a  linear 
foot  of  pipe  of  the  desired  size.  The  result 
will  be  the  number  of  linear  feet  of  pipe  re- 
quired. From  this  is  subtracted  the 
amount  of  radiation  supplied  by  the  flow  or 
feed  pipe  and  other  fittings. 

The  following  table  gives  the  radiating 
area  in  square  feet  of  a  linear  foot  of  pipe  of 
various  sizes. 

Radiating  surface  of 
Size  of  pipe  1  linear  foot 

}i  inch   0.27  square  feet 


1 

1/2 

2 

2/2 

3 

3/ 

4 


0.35 
0.43 
0.49 
0.62 
0.75 
0.91 
1.05 
1.18 


For  practical  purposes  the  following  gen- 
eral rule  will  give  approximately  the 
amount  of  radiating  surface  required.  Divide 
the    number    of    square    feet    of    glass    and 


HOT  WATER  INSTALLATION         176 
equivalent  glass : 

By  6  to  heat  the  house  to  40  degrees 
By  4  to  heat  the  house  to  50  degrees 
By  3.5  to  heat  the  house  to  60  degrees 
By  3     to  heat  the  house  to  70  degrees 

The  quotient  will  be  the  square  feet  of 
radiating  surface  required. 

Size  of  Flow  Pipe. — Having  determined 
the  amount  of  radiation  necessary,  the  next 
problem  is  to  determine  the  size  of  the  flow 
or  feed  pipe  required  to  supply  the  coils. 
Experience  has  shown  that  it  is  not  necessary 
for  the  supply  pipe  to  be  equal  in  capacity 
to  the  sum  of  the  capacities  of  the  coil  pipes. 
The  correct  size  may  be  determined,  theo- 
retically, by  the  use  of  the  following  rather 
tedious  formula: 

A=  ^^ 

25wvt 

In  this  formula  A=the  cross  section 
area  in  square  inches  of  the  flow  pipe; 
H,  the  total  radiation  in  B.  T.  U.  per 
hour  given  off  by  the  coils;  R,  the  radiating 
surface  in  square  feet;  w,  the  weight  of  the 
water  per  cubic  foot;  v,  the  velocity  of  feet 
per  second;  t,  the  difference  in  temperature 
between  the  water  when  it  leaves  the  boiler 
and  when  it  returns. 

This  formula  is  seldom  used  but  the  fol- 


176  GREENHOUSES 

lowing  table  has  been  derived  from  it.  To 
use,  measure  the  height  of  the  water  column 
in  feet,  find  from  the  table  the  factor  for  this 
height,  and  multiply  the  square  root  of  the 
radiating  surface  in  square  feet  by  this  fact- 
or. The  result  will  be  the  size  of  the  flow 
pipe,  in  inches  (diameter)  required.  This 
is  based  on  the  assumption  that  there  is  a 
difference  of  lo  degrees  in  temperature  be- 
tween the  water  when  it  leaves  and  when  it 
enters  the  boiler. 

Height  of 
Column  (ft.)  Diameter  Factor 

5   0.133 

10    0.113 

15  0.104 

20 0.095 

25   0.091 

30  0.187 

For  example,  to  supply  a  coil  of  ten  i/^- 
inch  pipes  lOO  feet  long  (500  square  feet) 
15  feet  above  the  bottom  of  the  boiler,  would 
require  a  feed  pipe  the  diameter  of  which 
would  be  represented  by  V500  x  0.104  equals 
22.4  X  0.104  equals  2.33  or  a  2y2-inch  pipe. 

Short  Methods. — The  above  formula 
takes  into  consideration  the  fact  that  the 
greater  the  height  of  the  column  of  water 
the  more  rapid  the  flow  and  consequently 


HOT  WATER  KXSTALLATION  177 

the  smaller  may  be  the  supply  pipe  used.  In 
greenhouse  heating,  however,  the  height  is 
seldom  ver}^  great,  usually  varying  between 
8  and  20  feet,  so  that  the  following  rule  of 
thumb  usually  proves  satisfactory.  The  flow 
pipe  should  be  one  pipe  size  greater  in  dia- 
meter (inches)  than  the  square  root  of  the 
radiating  surface  of  the  coil  (in  square  feet), 
divided  by   10.       Applying  this  rule  to  the 

above  problem  we  have  V5oo-^  10—2.24 
The  next  pipe  size  is  2/4  inches  but  this  is 
so  close  to  the  estimated  size  that  a  2>^-inch 
pipe  should  be  used  to  insure  efficiency. 

The  size  of  the  main  supply  pipe  from  the 
heater  is  determined  in  the  same  manner  by 
taking  the  sum  of  all  the  radiating  surface 
to  be  supplied.  It  is  better  to  have  one  main 
flow  pipe  leading  from  the  boiler,  from 
which  branches  to  the  various  coils  may  be 
taken,  than  to  have  a  flow  pipe  direct  from 
the  boiler  for  each  coil,  though  two  or  more 
flow  pipes  may  be  taken  off.  The  return 
pipes  should  be  of  the  same  size  as  the  flow 
pipes.  The  flow  pipe  is  taken  from  the  top 
of  the  boiler  and  the  return  pipe  enters  at 
the  bottom. 

In  Fig.  94  is  shown  a  diagram  of  a  method 
for  piping  a  medium-sized  house.    In  the  dia- 


178 


GREENHOUSES 


A  method  of  piping  a  medium  size  house 


gram  A  is  the  flow  pipe  extending  directly 
up  from  the  boiler;  B,  B,  branch  flow  pipes; 
C,  C,  branch  flow  pipes  extending  the  length 
of  the  house;  D,  D,  distributing  pipes  at  the 
opposite  end  of  the  house;  E,  E,  E,  E,  the  re- 
turn coils;  F,  F,  F,  F,  return  pipes;  and  G, 
expansion  tank. 

Valves  should  be  conveniently  placed  so 
that  any  or  all  of  the  coils  may  be  cut  off  in- 
dividually. They  may  be  placed  either  in  the 
flow  or  return  pipe,  or  in  both.  If  there  is  a 
valve  in  both  the  supply  and  return  from  each 
coil,  any  one  may  be  repaired  in  case  of  an 
accident  without  drawinsf  the  fire  or  inter- 


HOT  WATER  INSTALLATION 


179 


^      { 


^2>    ^ 


Fig.     95. — Diagram    showing    under-bench     method    of  hot 
water  piping.     A  and  B  flow  pipes;  C  and  D  heating  coils 

fering  with  the  circulation  in  the  other  coils. 
The  valves  should  be  of  a  type  which,  when 
open,  cause  as  little  resistance  to  the  flow  of 
water  as  possible. 


Length  of  Coils. — The  length  of  the  coils 
which  may  be  used  depends:  (i)  Upon  the 
height  of  the  column  of  water;  (2)  upon  the 
size  of  the  pipes  which  make  up  the  coils; 
and  (3)  the  amount  of  friction  in  the  coils 
and  fittings.  The  length  of  coils  which  may 
be  satisfactorily  used  with  pipes  of  various 
sizes  are  given  in  the  following  table. 


180  GREENHOUSES 

Size  of  pipe  Length  of  coil 

1  inch    Up  to     50  feet 

1^  inch  50  to     75  feet 

VA  inch  75  to  100  feet 

2  inch   100  to  150  feet 

This  table  is  based  on  the  supposition  that 
gravity,  only,  is  to  be  depended  upon  for 
circulation.      When  pumps  are  used  to  cir- 


Fig.  96. — Gasoline  engine  arran-ed  t( 
in    a    sfreenhouse    heatins. 


circulate  hot  'vvater 
system 


HOT  WATER  INSTALLATION         T81 

culate  the  water  the  length  may  be  materially 
increased. 

The  most  commonly  used  size  is  i>^-inch, 
and  when  the  houses  are  much  over  loo  feet 
in  length  two  or  more  coils  may  be  used, 
each  extending  only  a  part  of  the  length,  and 
having  separate  feed  and  return  pipes. 

Expansion  Tank. — Water  expands  in 
heating.  It  is  necessary,  therefore,  to  make 
some  provision  to  take  care  of  the  expan- 
sion, in  order  that  the  pipes  shall  not  burst 
and  to  keep  them  full  at  all  temperatures. 
This  is  accomplished  b}^  connecting  the  sys- 
tem with  an  expansion  tank  into  which  the 
excess  water  will  flow  as  it  expands,  and 
from  which  it  will  flow  back  into  the  system 
as  it  cools.  It  is  placed  at  or  above  the  high- 
est point  in  the  system,  but  it  may  be  con- 
nected with  any  part  of  the  system  or  even 
with  the  boiler. 

The  size  of  tank  required  is  directly 
proportional  to  the  volume  of  water  con- 
tained in  the  system  and  is  determined  by 
the  amount  of  expansion  resulting  from 
heating.  The  following  table. adapted  from 
Kent  shows  the  relative  amount  of  expansion, 


182 


GREENHOUSES 


Temperature  Temperature  Comparative 

Cent.  Fahr.  Volume 

4° 39.1° 1.00000 

10° 50.  ° 1.00O25 

20° 68.  ° 1.0O171 

30° 86.  ° 1.00425 

40° 104.  ° 1.00767 

50° 122.  ° 1.01186 

60° 140.  °  . . . .  .• 1.01678 

70° 158.  ° 1.02241 

80° 176.  ° 1.02872 

90° 194.  ° 1.03570 

100° 212.  ° 1.04332 


From  the  above  table  it  will  be  seen  that 
the  increase  in  volume  from  50  to  212  de- 


Fig.  97. — Automatic   expansion   tank.     This   is   con- 
nected  with   the    city   water    system    and    will   auto- 
matically keep   the  heating  system   filled.     See  also 
G,  Fig.  94 


HOT  WATER  INSTALLATION  183 

g-rees  is  LO4432 — 1.00025=0.04307,  or  a  little 
more  than  4  per  cent.  It  is  customary  to 
make  the  expansion  tank  large  enough  to 
hold  5  per  cent,  or  a  twentieth  of  the  water 
contained  in  the  system,  including  the  boil- 
er. Thus,  if  the  system  contains  100  gal- 
lons, the  supply  tank  should  be  large  enough 
to  hold  a  twentieth  of  that  amount  or  5 
gallons. 

The  capacity  in  gallons  of  a  linear  foot  of 
standard  wrought  pipe  is  shown  in  the  fol- 
lowing table. 

Size  of  pipe  Capacity  per 

diam.  in  inches  linear  foot 

1        0.1408   gallons 

VA   0.0638 

V/z   , 0.0918 

2       , 0.1632 

23^.  ....•  0.2550 

3  0.3672 

4 0.6528 

5  1.0200 

6  1.4690 

Pressure  Systems. — Water  in  an  open 
kettle  cannot  be  heated  above  212  degrees  at 
sea  level.  At  that  temperature  it  boils  and 
all  further  heat  energy  is  expended  in  vapor- 
izing the  water.  In  an  open  hot-water  heat- 
ing system  the  same  is  true,  except  that  the 


184 


GREENHOUSES 


slight  pressure  of  the  cohimn  of  water  in  the 
system  may  permit  the  water  in  the  boiler  to 
reach  a  temperature  slightly  above  212  de- 
grees. If  water  can  be  kept  under  pressure  it 
may  be  raised  to  almost  any  desired  tempera- 
ture, and  in  a  heating  system  this  would  mean 
less  necessary  radiating  surface.  The  boil- 
ing point  of  water  under  various  pressures 
above  normal  or  atmospheric  pressures  is 
shown  in  the  following  table: 

Pounds  pressure  Boiling  point 

Normal  212.0°   Fahr. 

H  pound  213.7° 

1  "  215.3° 

2  "  218.5° 

3  "  221.5° 

4  "  224.4° 

5  "  227.1° 

6  "  229.7° 

10        "  240.0° 

Several  systems  have  been  evolved  to  pro- 
duce pressure  in  a  heating  system.  One  of 
the  earliest  was  the  closed  tank  system  in 
which  the  expansion  tank  was  made  air-tight 
and  fitted  with  a  safety  valve  set  so  as  to  let 
the  air  in  the  tank  escape  at  a  certain  pres- 
sure. By  this  means  the  water  in  the  coils 
may  be  made  to  reach  a  temperature  con- 
siderably above  the  boiling  point, 


HOT  WATER  INSTALLATION 


185 


Recently  various  automatic  devices  using 
a  column  of  mercury  to  produce  the  same  re- 
sult have  been  placed  on  the  market.  One 
model  is  designed  to  be  placed  in  the  pipe 
leading  from  the  return  pipe  to  the  expansion 
tank,  the  tank  in  this  case  being  open.  The 
advantage  of  these  devices  over  the  closed 
tank  system  lies  in  the  fact  that  they  are 
less  likely  to  become  clogged  and  stick  than 
are  the  safety  or  pop  valves. 

In  action  these  so-called 
"generators"  operate  as 
follows :  The  pressure  is 
determined  by  the  height 
of  the  column  of  mercury- 
When  there  is  no  heat  in 
the  boiler  the  mercury  is 
in  the  position  shown  at  a, 
Fig.  98.  As  soon  as  the 
water  becomes  warm  it  ex- 
pands and  flows  in  through 
the  opening  x.  This  forces 
the  mercury  down  in  the 
cistern  and  up  through  the 
small  pipe  b.  The  amount 
of  mercury  is  so  arranged 
that  when  it  is  pushed 
down  to    the    level  of  the 


Fig.    98.— A    type 
of  mercury  "gen- 
erator" 


186  GREENHOUSES 

curve  in  the  outlet  pipe  at  c  it  overflows  at  d. 
This  allows  some  of  the  water  to  escape,  and 
this  goes  up  through  the  pipe  e  to  the  ex- 
pansion tank,  but  the  mercury  being  heavier 
falls  back  again  through  f  to  the  cistern. 

This  automatically  keeps  the  pressure  at 
any  predetermined  point,  usually  about  lo 
pounds,  which  makes  possible  the  heating  of 
the  water  to  a  temperature  of  240  degrees. 
This  makes  practical  the  heating  of  the  coils 
to  a  high  temperature  in  severe  winter 
weather  and  at  the  same  time  permits  the 
system  to  be  run  at  lower  temperatures  in 
mild  weather.  In  this  respect  it  has  the  ad- 
vantage over  steam.  It  is  claimed  for  these 
mercury  "generator"  devices  that  they 
greatly  improve  the  circulation  of  the  water 
in  a  heating  system. 

The  most  apparent  advantage  is  that  they 
make  possible  the  use  of  less  radiating  sur- 
face, hence  the  first  cost  is  less.  It  is  but 
fair  to  say  that,  as  a  rule,  growers  who  have 
installed  them  have  found  them  satisfactory. 
When  the  hot  water  is  circulated  by 
pumps  it  is  possible,  though  probably  not  de- 
sirable to  maintain  a  high  pressure.  Econ- 
omy in  heating  by  hot  water  lies  in  having 
abundant  radiating  surface  and  rapid  circu- 


HOT  WATER  INSTALLATION  187 

lation  and  then  keeping  the  water  at  a  mod- 
erate temperature. 

Caution. — In  any  system  see  that  the  ex- 
pansion tank  and  the  pipe  leading  to  it  are 
placed  where  they  will  not  freeze.  As  there 
is  ordinarily  no  circulation  in  the  water  they 
contain  they  will  freeze  if  placed  where  the 
temperature  falls  below  freezing.  The  re- 
sults will  almost  surely  be  (Jisastrous. 


CHAPTER  XII 

STEAM  INSTALLATION* 

General  Principles. — In  steam  heating 
there  is  no  circulation  in  the  same  sense  that 
there  is  in  hot  water  heating,  but  the  steam 
is  conducted  into  the  heating  coils,,  where  it 
condenses.  In  condensing  it  gives  up  its 
"latent"  heat.  The  water  of  condensation, 
which  occupies  only  about  0.017  part  of  the 
space  occupied  by  the  steam,  finds  its  way 
back  to  the  boiler  either  by  flowing  back 
through  the  supply  pipes,  or  through  return 
pipes  connected  with  the  opposite  ends  of  the 
coils.  The  latter  system  is  most  commonly 
used  in  greenhouse  heating. 

In  contrasting  steam  and  hot-water  heat- 
ing it  is  well  to  keep  in  mind  the  fact  that 
only  180  B.  T.  U.  are  required  to  raise  one 

*In  order  to  avoid  repetition  steam-  heating  is-  discussed 
largely  in  contrast  to  hot  water  'heating,  as  described 
in  the  preceding  chapter.  Both  chapters  .should  be 
read  by  one  wishing  to  inform  himself  on  steam 
heating. 

188 


STEAM  INSTALLATION  189 

pound  of  water  from  32  to  212  degrees  but 
that  966  B.  T.  U.  (usually  considered  as  1000) 
are  required  to  change  a  pound  of  water  at 
212  degrees  into  steam.  When  the  steam  is 
condensed  in  the  coils  it  gives  off  this  heat. 
This  is  known  as  the  latent  heat  of  steam.  It 
may  be  defined  as  the  amount  of  heat  ab- 
f orbed  in  changing  from  a  liquid  to  a  vapor 
or  the  amount  given  oft*  in  changing  from  a 
vapor  to  a  liquid  state. 

The  problem  in  steam  heating  is  to  supply 
CAi  amount  of  radiating  surface  sufficient  to 
condense  enough  steam  to  furnish  the 
amount  of  heat  required.  Under  ordinary 
greenhouse  conditions  a  square  foot  of  steam 
radiating  surface  may  be  counted  on  to  con- 
dense approximately  one  quarter  pound  of 
steam  per  hour.  Each  square  foot  of  radi- 
ating surface  will,  therefore,  provide  a  fourth 
of  960  or  approximately  240  B.  T.  U.  per 
hour. 

The  number  of  B.  T.  U.  required  per  hour 
to  heat  a  given  house  (see  page  172),  divided 
by  240  will  give,  therefore,  the  number  of 
square  feet  of  steam  radiation  required,  and 
from  the  table  on  page  174  the  number  of 
linear  feet  of  pipe  may  be  easily  determined. 
Assuming  a  steam  pressure  of  five  pounds 


190  GREENHOUSES 

per  square  inch  the  following  rule  will  be 
found  useful  in  determining  the  amount  of 
steam  radiation  required  for  a  house  when 
the  lowest  outside  temperature  to  be  ex- 
pected is  not  lower  than  zero. 

Divide  the  num'ber  of  square  feet  of  glass 
and  equivalent  glass. 

By  9  to  heat  house  to  40  degrees 
By  7  to  heat  house  to  50  degrees 
By  6  to  heat  house  to  60  degrees 
By  5  to  heat  house  to  70'  degrees 
The  quotient  will"  be  the  number  of  square  feet  of 
radiating   surface    required 

Size  and  Length  of  Coils. — There  is  less 
friction  in  steam  than  in  hot-water  heating, 
and  for  this  reason  smaller  pipes  may  be  used 
in  the  heating  coils.  They  are  seldom  larger 
than  1%-inch,  and  i%-inch  is  very  commonly 
used.  Even  i-inch  pipe  may  be  used  in 
comparatively  short  runs.  Smaller  pipes 
may  also  be  used  in  steam  than  in  hot-water 
heating,  for  the  rjeason  that  the  radiation  per 
square  foot  of  surface  is  greater  and  there- 
fore less  surface  is  required.  In  other  words, 
an  equal  number  of  smaller  pipes  or  a  small- 
er number  of  pipes  of  equal  size  may  be  used 
in  steam  than  in  hot-water  heating.  Small 
pipes  furnish  a  greater  amount  of  radiation 
in  comparison  to  their  cubic  capacity  than 


STEAM  INSTALLATION 


191 


do  large  pipes.     Large  cast-iron  pipes  are 
almost  never  used  in  steam  heating. 

When  i-inch  pipe  is  employed  coils  may  be 
safely  used  up  to  75  feet  in  length;  134- 
inch  up  to  150  feet;  and  i/^-inch  up  to  250 
feet.  As  with  hot  water,  better  results  and  a 
more  uniform  temperature  may  be  secured 
by  using  two  or  more  comparatively  short 
coils,  rather  than  one  which  is  excessively 
long.  In  small  houses  it  is  possible  to  run 
the  coils  entirely  around  the  house,  maintain- 
ing an  even  downward  slope. 

Arrangement  of  Coils. — As  indicated  in  a 
preceding  paragraph,  either  of  two  methods 
of  piping  may  be  used.  In  one  the  water 
resulting  from  the  condensation  of  the  steam 


Fig.  99. — A  corner  coil.     It  allows  for  expansion  of  the 
pipes 


1912 


GREENHOUSES 


Aqws  back  to  the  boiler  through  the  supply 
pipe.  In  this  case  all  pipes  have  an  upward 
slope  from  the  boiler,  with  no  sags  or  pock- 
ets in  which  the  water  can  collect.  This 
method,  sometimes  known  as  the  single  pipe 
system,  is  very  commonly  used  in  heating 
dwellings  where  the  pipes  are  mostly  verti- 


Fig.  100. — A  mortise  coil  designed  to  allow  for  expan- 
sion of  pipes 

cal,  but  in  greenhouses  having  long,  nearly 
horizontal  coils  there  is  likely  to  be  much 
hammering  in  the  pipes,  caused  by  the  in- 
terference of  the  steam  with  the  return 
water. 

A  more  satisfactory  method  for  green- 
house heating  is  to  arrange  the  pipes  much 
the  same  as  in  hot-water  heating,  pro- 
portioning the   size   to   the   supply   and   re- 


STEAM  INSTALLATION  193 

turn  pipes  according  to  directions  given  in 
a  following  paragraph.  This  is  known  as 
the  two-pipe  system.  The  return  pipe  en- 
ters the  boiler  below  the  surface  of  the  water. 
The  coils  should  have  a  fall  toward  the  boiler 
of  about  I  inch  to  20  feet.  It  is  not  wise 
to  use  the  straight  coils  commonly  used  for 
hot  water  in  steam  heating  as  they  do  not 
allow  for  the  unequal  expansion  of  the  pipes 
when  the  steam  is  turned  on  quickly.  In 
steam  heating  special  form  of  coils  are  com- 
monly used  among  which  are  the  corner  coil 
and  mortise  coil. 

Size  of  Supply  and  Return  Pipes. — Theo- 
retically, the  size  of  the  flow  and  return  pipes 
in  steam  heating  may  be  much  smaller  than 
in  hot-water  heating.  This  is  especially  true 
of  the  return  pipe,  since  the  water  which  it 
carries  occupies  only  0.017  of  the  space  oc- 
cupied by  the  steam  from  which  it  is  con- 
densed. In  practice,  however,  the  flow  or 
supply  pipe  for  steam  is  made  nearly  as  large 
as  for  hot  water  and  the  return  pipe  only 
slightly   smaller. 

The  following  table  shows  the  flow  of 
steam  in  pipes  of  different  sizes  at  a  pressure 
at  the  boiler  of  approximately  five  pounds. 


194:  GREENHOUSES 


Size  of 

pipe 

1^2  inches 

2 

" 

2^ 

<< 

3 

« 

3.^ 

<( 

4 

« 

4K. 

(< 

5 

<< 

6 

(< 

7 

« 

Pounds  of  steam  per  hour 

70 

138 

220 

390 

570 

800 

1000 

1400 

2200 

3200 


To  find  the  size  of  supply  pipe  required  it  is 
only  necessary  to  determine  the  number  of 
pounds  of  steam  condensed  per  hour  by  the 
coils  (approximately  one-quarter  pound  for 
every  square  foot  of  radiation)  and  from  the 
above  table  select  the  correct  size. 

The  following  table,  adapted  from  Carpen- 
ter, gives  the  size  of  supply  and  return  pipes 
recommended  to  be  used  in  the  two-pipe  sys- 
tem for  different  amounts  of  radiation, 
when  a  pressure  of  not  greater  than  five 
pounds  is  used. 

Sq.  ft.  of  radiation 
to  be  supplied     Size  of  supply  pipe  Size  return  pipe 

200 iy2  inch 1%  inch 

400 2        "     VA. 

700 2^     "     2 

1000 3        "     2 

1600 3-^    "     2^: 

2300 4        "     2^ 

3200 4^     "     2^ 


STEAM  INSTALLATION 


195 


4100 

5        "     ... 

3 

6500 

6        "     ... 

3 

9500 

7        "     ... 

3/. 

Valves. — In  steam  heating  it  is  essential 
that  each  coil  be  provided  with  a  cut-off 
valve.    This  is  even  more  essential  than  with 


Fig.  101. — Reducing  valve 


196  GREENHOUSES 

hot  water  since  with  steam  heating  the  tem- 
perature of  the  steam  must  be  at  least  212 
degrees,  while  with  hot  water  the  tempera- 
ture may  be  varied  according  to  the  weather. 
Automatic  air  valves  are  placed  at  the  high- 
est point  of  each  coil  and  also  in  the  supply 
pipes. 

High  Pressure  Heating. — When  steam 
above  five  pounds  pressure  is  used  it  is  known 
as  high  pressure  heating.  For  greenhouse 
purposes  high  pressure  heating  is  not  satis- 
factory, as  the  pipes  are  too  hot.  In 
large  establishments,  however,  a  high  press- 
ure is  often  maintained  at  the  boiler  and  is 
passed  through  a  reducing  valve  before  it 
enters  the  coils. 

Vacuum  and  Vapor  Systems. — Several 
heating  systems  are  now  on  the  market  which 
endeavor  to  give  to  steam  heating  some  of 
the  advantages  claimed  for  hot  water,  viz.,  a 
lower  temperature  of  the  heating  pipes  and 
less  frequent  attention  to  the  boiler.  They 
differ  from  straight  steam  heating  in  that  a 
partial  vacuum  is  maintained  within  the 
system,  thus  causing  the  water  in  the  boiler 
to  give  off  vapor  at  a  temperature  of  less 
than  212  degrees. 


STEAM  INSTALLATION  197 

There  are  several  different  systems  but 
they  may  all  be  grouped  roughly  into  three 
classes:  (i)  Those  in  which  a  vacuum  is 
created  by  means  of  a  pump  or  other  me- 
chanical device;  (2)  those  in  w^hich  the  air 
is  expelled  by  raising  the  steam  to  a  relative- 
ly high  pressure,  and  then  preventing  it  from 
returning  by  some  form  of  automatic  mer- 
cury seal,  and  (3)  those  in  v^hich  a  constant, 
though  slight,  vacuum  or  tendency  to  vac- 
uum is  maintained,  by  connecting  the  sys- 
tem with  the  chimney  and  utilizing  the  "pull" 
of  the  draft. 

These  systems  are  now  being  rapidly  in- 
stalled in  public  buildings  and  dwellings,  and 
no  doubt  will  be  found  more  satisfactory 
than  steam  for  greenhouses.  In  addition  to 
the  advantages  given  above  it  is  claimed  for 
these  systems  that  they  are  more  economical 
of  fuel  than  are  either  steam  or  hot  water, 
that  the  circulation  is  better  and  surer,  and 
also  that  there  is  no  trouble  arising  in  long 
runs  from  water  of  condensation. 

Arrangement  of  Boilers. — In  the  common 
gravity  system  of  steam  heating  the  boilers 
must  be  below  the  level  of  all  mains  and 
coils,      When  thev  cannot  be   so-  located, 


198  GREENHOUSES 

special  devices  to  be  described  later  must 
be  employed  to  return  the  water  of  conden- 
sation. As  with  hot  water,  two  or  more 
boilers  should  be  provided,  rather  than  one 
large  one,  to  allow  for  repairs  in  case  of  ac- 
cident and  for  use  in  severe  weather  to  avoid 
the  necessity  of  forcing. 

Steam  Pumps  and  Traps. — As  suggested 
in  the  preceding  paragraph,  it  is  sometimes 
impossible  or  inconvenient  to  place  the  boil- 
er below  the  level  of  the  heating  coils.  This 
is  especially  true  in  large  establishments,  re- 
quiring large  boilers  using  large  quantities 
of  fuel.  In  order  to  return  the  water  of  con- 
densation in  such  cases  steam  return  traps 
and  steam  pumps  are  used.  Their  use  is  al- 
so necessary  where  a  higher  pressure  is  car- 
ried at  the  boiler  than  in  the  coils. 

The  return  trap  is  a  contrivance  which  is 
automatic  in  its  action,  and  which  overcomes 
the  back  pressure  from  the  boiler  by  an  in- 
genious method  of  equalizing  the  difference 
in  pressure  between  the  boiler  and  the  coils. 
Being  automatic  in  its  action  and  requiring 
but  little  attention  it  has  been  quite  gener- 
ally used.  Steam  pumps,  on  the  other  hand, 
require  considerable  attention,  though  they 


STEAM  IXSTALLATK3N 


199 


are  less  complicated  than  the  return  traps. 
A  small,  separate  hoiler  is  generally  used  to 
operate  the  pump,  and  the  exhaust  and  sur- 
plus steam  is  turned  into  the  g-eneral  heat- 
ing system  after  being  reduced  to  low  pres- 
sure. Gas  and  electric  motors  are  also  used 
to  drive  the  pumps  for  returning  the  water 
of  condensation. 


Fig.  102.— A  type  of  steam  return  trap 


CHAPTER  XIII 
BOILERS,  FUELS  AND  FLUES 

The  terms  boiler  and  heater  as  used  in  dis- 
cussing greenhouse  heating  systems  are 
synonymous.  It  is  customary,  however,  to 
speak  of  a  steam  heating  apparatus  as  a 
''boiler"  and  of  a  hot-water  heating  appar- 
atus as  a  ''heater,"  probably  because  in  steam 
heating  the  water  boils,  while  in  hot-water 
heating  it  is  not  supposed  to  boil.  It  often 
occurs,  however,  that  the  same  kind  of  heat- 
ing apparatus  is  used  in  both  steam  and  hot- 
water  heating  with  no  essential  changes,  ex- 
cept in  the  accessories.  In  this  chapter  the 
term  boiler  will  be  applied  to  both  steam  and 
hot-water  heating  devices. 

The  boilers  used  in  greenhouse  heating 
differ  but  little  from  those  used  in  heating 
other  buildings.  In  fact  the  same  makes 
and  styles  of  boilers  are  very  frequently  used 
for  both  purposes.  Certain  manufacturers 
have,  however,  made  a  thorough  study  of 
greenhouse  heating  and  have  developed  boil- 

200 


BOILERS,  FUELS  AND  FLUES  201 

ers  with  this  particular  end  in  view.  In 
buying  a  boiler  the  safe  plan  is  to  purchase 
a  style  which  has  fully  established  itself  on 
the  market  and  which  is  made  by  a  thorough- 
ly reliable  firm.  Such  boilers  will  have  passed 
the  experimental  stage  and  repairs  may  be 
secured  quickly  and  reasonably. 

Essentials  of  a  Boiler. — The  function  of 
the  boiler  is  to  extract  the  latent  heat  from 
the  fuel  and  transfer  it  to  the  water  or  steam, 
which  may  be  circulated  when  needed.  The 
essentials  are,  a  grate  on  which  the  fuel  is 
burned  and  a  watertight  receptacle,  so  ar- 
ranged as  to  present  a  large  amount  of  sur- 
face (known  as  fire  surface)  to  the  fire  or 
burning  gases.  The  problem  of  the  manu- 
facturer is  to  so  arrange  and  proportion  the 
fire  surface  and  the  grate  surface  that  the 
heat  of  the  burning  fuel  may  be  most  econ- 
omically absorbed  and  distributed. 

Grate  Surface. — For  best  results  the 
amount  of  grate  surface  should  be  large 
enough,  so  that  the  fire  will  not  have  to  be 
forced.  In  small  and  medium-size  boilers 
the  rate  of  combustion  should  not  exceed 
from  five  to  seven  pounds  of  coal  per  square 
foot  of  grate  per  hour.  In  larger  boilers  the 
rate  of  combustion  of  fuel  may  be  as  high  as 


202  GREENHOUSES 

from  six  to  ten  pounds  per  square  foot  per 
hour. 

A  pound  of  best  coal  has  a  heating  value 
of  about  14,000  B.  T.  U.  per  pound,  of  which 
only  about  60  per  cent,  or  8,400  B.  T.  U.  are 
utilized  in  heating  water  or  producing 
steam.  It  is  the  usual  practice  to  estimate 
that  each  pound  of  coal  will  impart  about 
8,000  B.  T,  U.  to  the  heating  medium,  and 
that  each  square  foot  of  grate  surface  will 
burn  about  six  pounds  of  coal  per  hour.  This 
gives  48,000  B.  T.  U.  per  square  foot  of  grate 
surface  per  hour. 

To  find  the  approximate  number  of  square 
feet  of  grate  surface  required  to  heat  a  given 
house,  find  the  number  of  heat  units  re- 
quired, by  the  method  described  in  Chapter 
XI,  and  divide  by  48,000. 

In  general,  a  square  foot  of  grate  surface 
is  sufficient  to  supply  250  square  feet  of 
radiating  surface. 

Fire  Surface. — Fire  surface  (sometimes 
known  as  heating  surface  or  water  surface) 
is  of  two  kinds;  direct  and  indirect.  The 
direct  fire  surface  is  that  immediately  above 
or  around  the  fire,  against  which  the  light 
of  the  burning  fuel  shines.  Indirect  fire  sur- 
face is  that  which  receives  the  heat  from  the 


BOILERS,  FUELS  AND  FLUES  203 

', burning  gases  on  their  way  to  the  chimney. 
Direct  fire  surface  is  three  times  as  effective 
as  indirect.  It  does  not  follow,  however, 
that  boilers  having  the  greatest  amount  of 
direct  fire  surface  are  the  most  efificient,  for 
there  must  be  sufficient  length  of  fire  travel 
to  consume  the  gases  and  enable  them  to  give 
up  the  greater  part  of  the  heat  of  combus- 
tion to  the  water. 

To  be  most  effective  the  fire  surface  is  so 
arranged  that  the  heat  will  impinge  at  right 
angles  against  it.  This  is  accomplished  with- 
out serious  interference  with  the  draft, 
and  without  making  the  course  of  the  water 
in  the  boiler  so  long  and  tortuous  as  to  in- 
terfere with  its  rapid  circulation.  The  pro- 
portion of  fire  surface  to  grate  surface  dif- 
fers so  widely  in  the  different  forms  of  boil- 
er construction  that  no  definite  rule  can  be 
given.  It  may  vary  from  15  to  35  square 
feet  to  each  square  foot  of  grate  area. 

Types  of  Boilers. — Broadly  speaking, 
there  are  three  types  of  boilers,  when  classi- 
fied as  to  their  form  of  construction :  ( i )  Boil- 
ers in  which  the  water  is  spread  out  in  thin 
sheets  between  layers  of  iron  or  steel  and 
against  which  the  heat  strikes;  (2)  tubular 


204 


GREENHOUSES 


boilers  in  which  the  burning  gases  travel 
through  tubes  or  flues  which  are  surrounded 
by  water;  and  (3)  water-tube  boilers  in 
which  the  water  is  contained  in  tubes  about 
which  the  burning  gases  circulate.       Manv 


Fig.  103. — A  type  of  "vertical"'  or 
"square"   sectional   boiler 

manufacturers  combine  two,  and  sometimes 
all,  of  the  above  types  in  one  boiler.  The 
two  latter  types  are  more  commonly  used 
for  power  purposes  than  is  the  first,  but  for 
heating  establishments  of  moderate  size  a 
modification  of  the  first  is  widely  used. 


BOILERS,  FUELS  AND  FLUES 


205 


Cast    and    Wrought-Iron    Boilers. — The 

cast-iron  boiler  has  a  size  limit  above  which 
it  is  impracticable  to  go,  though  two  or  more 
may  be  joined  in  a  series.  It  is  also  claimed 
that  on  account  of  the  thickness  of  the  walls 


Fig.  104. — End  view  of  "square"  sectional 

boiler  showing  fire  travel.     A  and  B,  push 

nipples    for    joining    sections 

it  is  less  economical  of  fuel  than  are  wrought- 
iron  boilers,  which  have  thinner  walls.  On 
the  other  hand,  cast-iron  boilers  do  not  rust 
as  badly  as  wrouQ:ht-iron  ones  when  not  in 
use,  and  they  have  no  flues  to  be  burned  out 
by  the  sulphurous  gases  resulting  from  the 


206  GREENHOUSES 

use  of  the  poorer  grades  of  coal.  But  they  do 
sometimes  crack,  and  they  have  a  disgusting 
way  of  doing  it  at  the  most  inopportune 
moment. 


^„ 


Fig.   105. — Side  view   of  ''square"   sectional  boiler 
showing  fire  travel 

Where  fuel  is  cheap  and  abundant,  and 
especially  in  small  ranges,  or  where  the  boiler 
is  in  a  damp  basement  and  likely  to  be  neg- 
lected during  the  summer,  cast-iron  boilers 
are  likely  to  give  better  satisfaction  than 
wrought-iron.  In  large  establishments  of 
100,000  feet  or  over,  large  wrought-iron  tubu- 


BOILERS,  FUELS  AND  FLUES  207 


208 


GREENHOUSES 


lar  or  water-tube  boilers  are  almost  always 
used. 

Styles  of  Cast-iron  Boilers. — There  are 
three  general  types  or  styles  of  cast-iron 
boilers.  The  most  popular  is  the  "vertical"  or 

*'square"sectional  boil- 
er. The  advantages 
claimed  for  these  forms 
of  boilers  are:  (i) 
They  may  be  enlarged 
by  adding  extra  sec- 
tions; (2)  a  break  or 
crack  will  usually  be 
confined  to  one  sec- 
tion; and  (3)  they  may 
be  made  in  large  sizes 
because  the  individual 
castings  are  compara- 
tively small  and  light. 
The  sections  are  joined 
together  by  accurate- 
ly ground  push  nip- 
ples or  by  screw  nipples.  Probably  80  per 
cent,  of  the  cast-iron  boilers  now  being 
placed  in  greenhouses  of  moderate  size  are 
of  this  general  type- 

A  second  style  of  cast-iron  boiler  is 
known  as  ''horizontal''  or  "round''  sectional 
boiler.     It  gives  good  satisfaction  in  small 


Fig.       107.— A      type      of 

"round"     or     "horizontal" 

sectional  boiler 


BOILERS,  FUELS  AND  FLUES 


209 


arge  sizes.     In 


ranges  but  is  not  made  ni 
a  third  style  there  are  no  sections,  but  the 
boiler  proper  is  cast  in  one  piece.  For  this 
reason  its  size  is  limited.  It  is  also  open 
to  the  disadvantage  that  a  crack  will  spoil 
the  whole  boiler.     It  is  little  used  at  present. 


Fig.   108. — Corrugated   fire  box  -boiler.     The   boiler 
proper    is    of    a    single    casting 

Styles  of  Wrought-Iron  Boilers. — Most 
wrought-iron  boilers  are  either  tubular  or 
water-tube  in  construction,  though  the  tubes 
or  flues  are  sometimes  connected  with  cast- 
iron  headers.  A  new  type  of  wrought-iron 
boiler  is  now  being  extensively  advertised  for 
greenhouse  heating.  It  is  claimed  for  this 
type  that  it  steams  more  quickly  than  the 


210 


GREENHOUSES 


Fig.    109. — Type    of   tubular   boiler   much   used   in   green- 
house heating 

tubular  boilers  and  that  it  is  much  more  dur- 
able. As  a  rule  users  seem  to  be  well  satis- 
fied with  it. 

Steam  and  Hot-water  Boilers. — As  usually 
constructed,  low-pressure  steam  boilers  dif- 
fer but  little  in  construction  from  hot  water 
boilers.  The  essential  difference  is  that  in 
steam  boilers  provision  is  made  for  a  steam 
chest  or  storage  above  the  water  line,  while 
in  hot-water  boilers  the  space  between  the 
top  of  the  tubes  and  the  top  of  the  boiler  is 
so  small  that  there  is  no  room  for  an  adequate 
steam  storage.     This  is  equivalent  to  saying 


BOILERS,  FUELS  AND  FLUES 


211 


^y/^^^^^^^r           ;,       ;•  jWl^H 

ofL            --  1 

'"/^^H^^^^^^^HHSiH 

|^^~n-7« 

1  ^^I^^^^^I^^Ih 

p.  :4 

^  ^      ., .                                               V.i^'^T-^^ll^Mi 

^-..  _. 

Fig,    110. — Battery   of  two  marine  type   boilers  used   for 
greenhouse  heating 

that  a  steam  boiler  may  be  used  for  hot-water 
heating,  but  that  a  hot-water  boiler  is  rare- 
ly satisfactory  for  steam  heating.  Large 
steam  boilers  are  quite  frequently  used  in 
hot-water  heating  when  equipped  with  the 
necessary  fittings  which  are  described  in 
a  succeeding  paragraph. 

Boilers  for  Soft  and  Hard  Coal. — Hard  coal 
burns  with  a  "short"  flame,  and  much  less 
fire  travel  is  required  to  burn  the  gases  than 
when  soft  coal,  which  burns  with  a  ''long" 
flame,  is  used.  More  flue  way  is  also  re- 
quired for  soft  coal  and  the  grates  are  more 
open.       Most  greenhouse  boilers  which  are 


212 


GREENHOUSES 


designed  for  soft  coal  will  burn  hard  coal 
equally  well.  If  they  are  designed  primarily 
for  hard  coal  they  will  not  burn  soft  coal 
efficiently.  More  grate  surface  is  required 
for  soft  coal  than  for  hard  coal,  because  it  is 


Fig.    111. — Wronght-iroii   boiler   without    flues 

more  bulky  weight  for  weight.  Most  mod- 
ern greenhouse  boilers  will  burn  either  hard 
or  soft  coal,  but  a  larger  size  will  be  required 
for  soft  coal  than  for  anthracite. 

Boiler  Ratings. — An  approximate  idea  of 
the  size  of  boiler  needed  may  be  found  by 
figuring  the  amount  of  grate  surface  by  the 
method  described  on  page  202.     Boiler  manu- 


BOILERS,  FUELS  AND  FLUES 


213 


facturers,  however,  rate  their  boilers  show- 
ing their  capacity.  Some  give  the  number 
of  square  feet  of  glass  that  they  will  heat  to 
a  given  temperature;  others  give  the  number 


Fig.  112. — Sectional  view  of  boiler  shown  in  Fig.  HI 

of  linear  feet  of  radiating  pipe  of  a  given 
size  which  they  will  supply;  and  still  others, 
especially  the  manufacturers  of  large  tubu- 
lar boilers,  give  the  capacity  of  their  boilers 
in  terms  of  horse-power. 

Since  different  manufacturers  often  ques- 
tion the  correctness  of    the    ratings  of  their 


214  GREENHOUSES 

competitors,  it  is  but  fair  that  buyers 
should  be  recommended  to  exercise  consider- 
able caution.  Probably  most  boilers  will, 
under  favorable  conditions,  develop  the  num- 
ber of  heat  units  for  which  they  are  rated, 
but  for  the  sake  of  safety  and  to  prevent  the 
necessity  of  forcing,  it  is  best  to  select  boil- 
ers with  ratings  at  least  20  per  cent,  in  ex- 
cess of  the  theoretical  needs. 

When  boilers  are  rated  according  to  the 
number  of  linear  feet  of  radiating  pipe  they 
will  supply,  it  is  usually  given  in  terms  of 
either  3%-inch  cast-iron  pipe  or  in  2-incli 
wrought-iron  pipe.  The  following  table 
gives  the  length  of  pipes  of  other  sizes  equiv- 
alent to  I  linear  foot  of  2  and  31/2-inch  pipe. 

1  ft.  of  2rV2  in.  C.I.-  pipe  equals.. 3.04    ft.  1  in.  W.I.  pipe 

1  ft.  oiZVi  in.  C.I.  pipe  equals.. 2.41     ft.  1^  in.  W.I.  pipe 

1  ft.  of  TrYz  in.  C.I.  pipe  equals.. 2.10    ft.  VA  in.  W.I.  pipe 

1  ft.  of  3^  in.  C.I.  pipe  equals..  1.68    ft.  2  in.  W.I.  pipe 

1  ft.  of  3-^  in.  C.r.  pipe  equals.. 1.39    ft.  2'>^  in.  W.I.  pipe 

1  ft.  of  2  in.   W.I.  pipe  equals. .  1.806  ft.  1  in.  W.I.  pipe 

1  ft.  of  2  in.   W.I.  pipe  equals'.  .1.431  ft.  1^4  in.  W.I.  pipe 

1  ft.  of  2  in.    W.I.  pipe  equals.  .1.25     ft.  VA  in.  W.I.  pipe 

Most  boiler  ratings  are  given  for  a  mini- 
mum outside  temperature  of  zero  degrees, 
Fahrenheit.  For  localities  subject  to  a  tem- 
perature of  lo  degrees  below  zero  a  boiler 
of  lo  per  cent,  greater  capacity  should  be  se- 


BOILERS,  FUELS  AND  FLUES 


215 


cured,  and  for  localities  subject  to  a  tem- 
perature of  20  degrees  below  zero,  a  boiler  of 
20  per  cent,  greater  capacity  should  be  se- 
cured. 

The  term  horse-power,  as  applied  to  boil- 
ers, represents  the  energy  developed  in  evap- 
orating 34.5  pounds  of  water  per  hour  from 
a. temperature  of  212  degrees,  or  the  develop- 
ment of  33,317  B.  T.  U.  per  hour.  Roughly, 
a  heating  boiler  will  supply  100  square  feet 
of  radiation  for  each  horse-power  which  it 
develops. 


Fig.    113. — Altitude    guage    for    hot 
water  boiler 

Boiler  Accessories. — It  has  already  been 
stated  that  a  steam  boiler  may  be  used  for 
hot-water  heating  by  simply  changing  the 
fittings.     When  used  for  hot-water  heating 


216 


GREENHOUSES 


the  boiler  is  fitted  with  an  altitude  gauge, 
which  shows  the  height  of  the  water  in  the 
system;  also  with  a  thermometer  to  show  the 
temperature  of  the  water.  A  valve  is  pro- 
vided for  draining  the  boiler  and,  if  desired, 
an  automatic  damper  regulating  device  may 
be  installed. 

When  used  for  steam 
heating  the  boiler  is  only 
partially  filled  with  water, 
and  a  water  column  and 
guage  is  necessary  to  indi- 
cate the  height  of  the 
water.  A  steam  guage  is 
also  necessary  to  indicate 
the  pressure;  and  a  safety 
valve  to  automatically  re- 
lieve the  pressure,  if  it  be- 
comes too  great  for  safety. 
Steam  boilers  are  usually 
Id  guage  Tor  equipped  with  automatic 
damper  regulators.  They 
are  rather  more  efficient  than  the  regulators 
used  on  hot-water  boilers.  A  drainage  valve 
is  provided  the  same  as  for  hot-water  boil- 
ers. Many  states  require  that  all  steam  boil- 
ers be  equipped  with  a  fusible  plug,  which  is 
simply  a  brass  plug  with  a  tin  core,  which 


Fig.  114— Water  col- 
umn   an( 

steam  boilers 


BOILERS,  FUELS  AND  FLUES 


21' 


Fig.  115. — Steam  guage 

is  screwed  into  a  hole  in  the  boiler  near 
the  bottom.  If  the  water  level  falls  below 
the  plug  the  heat  melts  it  out,  thus  making 


Fig.  116. — Diagram  of  automatic  damper  regulator.    The 

steam  pressure  acts  against  a  flexible  diaphram  which 

is  connected  with  the  dampers  by  means  of  a  lever  and 

chain 


218 


GREENHOUSES 


an  opening  and  lessening  the  danger  of  an 
explosion. 

The  boiler  and  all  pipes,  except  those  in 
the  greenhouse  itself,  should  be  insulated  as 
much  as  possible  to  prevent  loss  of  heat.  The 
best  known  material  for  this  purpose  is  as- 
bestos. For  coating  boilers  it  may  be  had 
in  a  granular  form,  which  is  mixed  with 
water  and  applied  with  a  trowel  or  the  bare 
hands.  For  covering  pipes  molded  casings 
may  be  had  to  fit  all  sizes  of  pipe. 


Fig.    117. — Asbestos   pipe   covering 

FUELS 

Coal  is  used  almost  universally  for  fuel  in 
greenhouse  heating,  except  in  sections  where 
natural  gas  or  oil  are  cheap  and  abundant. 
Gas  is  an  ideal  fuel,  but  somewhat  treach- 
erous inasmuch  as  the  pressure  is  likely  to  be 
lowest  in  the  coldest  weather.  Care  should 
be  taken  to  see  that  there  are  no  leaks,  as  it 
is  very  explosive,  and  it  is  also  poisonous  to 
vegetable  as  well  as  animal  life. 

Broadly   speaking,   coal  is   of  two  kinds, 


BOILERS,  FUELS  AND  FLUES  219 

anthracite  or  hard  coal,  and  bituminous  or 
soft  coal.     Hard  coal  burns  with  little  smoke 


Fig".   118. — Boiler  equipped  for  using  natural  ga.-. 

and  is  much  heavier  than  soft  coal,  although 
it  may  not  develop  as  much  heat  per  ton. 


220  GREENHOUSES 

It  is  easier  and  cleaner  to  handle,  and  re- 
quires less  attention  in  firing,  but  in  rnost 
sections  is  more  expensive. 

Soft  coals  are  of  two  general  types;  The 
free  burning  and  the  coking.  The  latter 
fuses  together  in  burning  and  is  somewhat 
more  difficult  to  handle  in  the  furnace  than 
the  free  burning,  though  it  is  preferred  by 
some  firemen. 

The  heating  value  of  a  coal  depends  upon 
the  percentage  of  total  combustible  matter 
contained,  and  upon  the  heating  value  per 
pound  of  the  combustible  portion.  In  some 
semi-bituminous  coals  the  heating  value  runs 
as  high  as  15,750  B.  T.  U.  per  pound.  The 
heating  value  of  a  few  common  types  of 
coals  as  given  by  Kent  are  shown  in  the  fol- 
lowing table. 

Kind  of  coal                 B.T.U.  Kind  of  coal                 B.T.U. 

Anthracite  Cambria    Co.,    Pa.    ...14450 

Northern   Coal  field    ..13160  Somerset    Co.,    Pa.    ...14200 

East    Middle    field    . . .  13420     Cumberland,    Md 1440O 

West   Middle   field    ...12840     Pocahontas,   Va 15070 

Southern    field    13220     Brier   Hill,    0 13010 

Scott  Co.,  Tenn 13700 

Semi-'bituminous  gj^    ^^^^^^    jl^ j2420 

Clearfield  Co.,   Pa.    ...14950     Missouri    12230 

Soft  coal  is  more  commonly  used  in  green- 
houses than  is  hard  coal.     This  is  especially 


BOILERS,  FUELS  AND  FLl'ES  221 

true  in  large  establishments.  The  price 
varies  with  the  quality,  distance  from  the 
mines,  etc. 

The  average  cost  for  soft  coal  to  6i  grow- 
ers, living  east  of  the  Mississippi  River,  for 
the  season  of  191 1-12,  was  $2.1,7,  per  ton.  The 
average  amount  used  for  the  season  was  11.6 
tons  for  each  1,000  square  feet  under  glass. 

Underfed  Boilers. — The  term  "underfed" 
is  applied  to  a  method  of  stoking,  in  which 
the  coal  is  fed  from  the  bottom  instead  of 
the  top  of  the  furnace.  It  is  claimed  for 
this  system  that  it  insures  a  more  perfect 
combustion  and  that  cheaper  grades  of  coal 
may  be  used.  Boilers  emplo^dng  this  prin- 
ciple have  not  come  into  very  general  use  in 
greenhouse  heating,  probably  because  they 
will  not  handle  successfully  all  grades  of 
coal. 

Self-stoking  Boilers. — Stoking  devices  are 
practical  only  in  large  establishments  us- 
ing large  boilers.  There  are  several  types, 
some  of  wdiich  w^ork  on  practically  the  same 
principle  as  the  underfed  furnaces  mentioned 
above,  except  that  their  action  is  automatic. 
In  other  forms  the  grate  bars  are  arranged 
in  the  form   of  an   endless   chain,   which   is 


222  GREENHOUSES 

moved  slowly  from  the  front  to  the  rear 
of  the  fire-box  by  means  of  gearing.  It  is 
claimed  for  the  self-stoking  devices  that  they 
not  only  save  labor,  but  that  they  are  more 
economical  in  the  use  of  fuel  than  is  hand 
stoking. 

Points  to  Consider. — The  following  points 
should  be  kept  in  mind  in  selecting  a  green- 
house heating  boiler: 

1.  It  should  be  of  ample  size — at  least  one 
size  larger  than  is  theoretically  necessary. 

2.  The  fire-box  should  be  deep  and  spac- 
ious. This  is  especially  true  of  boilers  for 
small  establishments  where  a  regular  fire- 
man is  not  employed. 

3.  The  combustion  chamber  (the  chamber 
above  the  grate)  should  be  large  enough  to 
insure  thorough  combustion  of  the  gases. 

4.  The  boiler  should  be  so  arranged  that 
it  may  be  easily  cleaned,  especially  the  flues 
and  heating  surfaces. 

5.  The  grates  should  be  heavy  but  easy 
to  operate  and  easily  removable,  so  that  re- 
pairs may  be  made  quickly. 

6.  The  water  travel  should  not  be  so  cir- 
cuitous as  to  prevent  of  rapid  circulation. 

7.  There  should  be  no  packed  joints.    All 


BOILERS,  FUELS  AND  FLUES  223 

.  unions  should  be  made  with  push  or  screw 
nipples. 

8.  Soft  coal  burners  require  a  somewhat 
different  construction  than  do  hard  coal  burn- 
ers. The  kind  of  fuel  to  be  burned  should 
be  clearly  in  mind  when  selecting  a  boiler. 

9.  The  ash  pit  should  be  deep  and  com- 
modious. Shallow  ash  pits  are  likely  to  be- 
come filled  so  that  the  draft  is  impaired 
and  the  grate  bars  ruined. 

CHIMNEYS  AND  FLUES 
A  very  essential  part. of  the  heating  equip- 
ment is  the  chimney  or  flue.  Its  purpose  is 
twofold:  First,  to  create  a  draft  in  order 
to  furnish  air  to  promote  combustion;  and 
second,  to  carry  off  smoke  and  gas.  The 
size  and  height  of  the  chimney  required  de- 
pends on  the  size  of  the  grate  surface.  Mere 
velocity  does  not  necessarily  indicate  that 
the  draft  is  sufficient ;  the  chimney  must  be 
of  sufficient  size  to  carry  the  required 
quantity. 

The  velocity  of  the  gas  in  the  flue  depends 
on  the  height  of  the  flue  and  upon  the  tem- 
perature of  the  gas.  The  difference  be- 
tween the  weight  of  the  hot  gases  in  the 
chimney,  and  a  column  of  cold  air  of  equal 


224 


GREENHOUSES 


size  outside  creates  a  flow  upward  in  the 
chimney.  This  difference  increases  with  the 
height  of  the  chimney,  and  if  the  difference 
in  temperature  increases  the  velocity  is  more 
rapid.  Locations  high  above  sea  level  require 
higher  chimneys  than  those  near  sea  level, 
on    account    of    the    rarety    of    the    atmo- 


Fig.  119. — Chimneys  should  extend  above  the  roofs  of 
adjacent    buildings 

sphere.  For  example,  at  Denver,  Col.,  (5,300 
feet)  the  height  should  be  about  20  per  cent, 
greater  than  at  sea  level. 

Chimneys  should  be  vertical  if  possible  and 
the  inside  should  be  smooth  and  free  from  all 
obstructions.  They  should  also  extend  well 
above  the  roofs  of  adjacent  buildings,  particu- 
larly when  there  is  danger  of  a  "down 
draft."  Round  chimneys  present  less  sur- 
face per  cubic  capacity  than  do  square  chim- 
neys, and  are  thus  more  efficient.  For  the 
same  reason  square  flues  are  better  than  ob- 
long flues. 


BOILERS,  FUELS  AND  FLUES  225 

The  following  table  shows  the  size  and 
height  of  chimneys  required  by  steam  boil- 
ers. For  hot-water  boilers  multiply  the  radi- 
ating surface  by  1.5. 

Height  of  chimney  in  feet 


Sq.ft. 

20 

30 

40 

50 

60 

80 

100 

120 

st'm  rac 

1.    Si2 

:e  of  Chimney 

(dia. 

or  1  sic 

le  sq.) 

in  incl 

ICS 

250 

7.4 

7.0 

6.7 

6.4 

6.2 

6.0 

6.0 

6.0 

500 

9.6 

9.2 

8.8 

8.2 

8.0 

6.6 

7.2, 

7.0 

750 

11.3 

10.8 

10.2 

9.6 

9.3 

8.8 

8.5 

8.2 

1000 

12.8 

12.0 

11.4 

10.8 

10.5 

10.0 

9.5 

9.2 

1500 

15.2 

14.4 

13.4 

12.8 

12.4 

11.5 

11.2 

10.8 

2000 

17.2 

16.8 

15.2 

14.5 

14.0 

13.2 

12.6 

12.1 

3000 

20.6 

18.5 

18.2 

17.2 

16.2 

15.8 

15.8 

14.4 

40O0 

23.6 

22.2 

20.8 

19.6 

19.0 

17.8 

17.0 

16.3 

5000 

26.0 

24.6 

23.0 

21.6 

21.0 

19.4 

18.6 

18.0 

6000 

28.4 

26.8 

25.0 

23.4 

22.8 

21.2 

20.2 

195 

7000 

30.4 

28.8 

27.0 

25.5 

24.4 

23.0 

21.6 

20.8 

8000 

32.4 

30.6 

28.6 

26.8 

26.0 

24.2 

23.4 

22.2 

9000 

34.0 

32.4 

30.4 

28.4 

27.4 

25.6 

24.4 

23.4 

10000 

27.0 

34.0 

32.0 

34.0 

28.6 

27.0 

25.4 

24.6 

15000 

. .  . 

. .  . 

38.4 

36.2 

35.0 

33.0 

31.0 

29.2 

20000 

.. 

43.0 

42.0 

41.0 

37.0 

35.0 

34.0 

30000 

. .  . 

. .  . 

50.0 

48.0 

46:0 

43.0 

41.0 

CHAPTER  XIV 
WATER   SUPPLY   AND    IRRIGATION 

An  abundant  supply  of  water  at  a  reason- 
able cost  is  necessary  for  the  successful  op- 
eration of  a  commercial  range  of  green- 
houses. Figures  compiled  from  the  experi- 
ence of  several  growers  show  that  the  con- 
sumption of  water  by  a  vegetable  crop  in  a 
greenhouse  during  the  bright,  hot  days  of 
June  and  July  may  be  as  high  as  280  gallons 
per  day  per  1000  square  feet  of  crops.  As 
the  watering  is  done  over  a  period  of  not 
more  than  three  or  four  hours  per  day,  it  is 
necessary  to  make  arrangements  to  supply 
the  maximum  amount  needed  during  that 
length  of  .time,  rather  than  during  the  24 
hours  of  the  day  as  is  usually  figured  for 
domestic  purposes. 

When  city  water  is  available  at  a  reason- 
able price  it  IS  doubtful  if  it  will  pay  the 
small  grower  to  go  to  the  expense  of  pro- 
viding a  private  supply.  Sometimes,  how- 
ever, the  conditions  are  such  that  a  private 

226 


IRRIGATION 


527 


supply  of  water  may  be  had  at  small  expense 
from  springs,  ponds  or  streams.  In  larger 
establishments  it  may  be  cheaper  to  install  a 
private  system  than  to  depend  on  city  water. 
Often,  also,  the  ranges  are  located  out- 
side the  city  limits  where  city  water  can- 
not be  had.     Data  based  on  the  reports  of 

nearly  lOO  florists  and 
vegetable  growers 
show  that  the  average 
cost  per  i,ooo  gallons 
of  city  water  is  i8 
cents,  and  that  the 
average  cost  of  the 
home  supply,  includ- 
ing cost  of  equipment, 
depreciation  and  main- 
tenance, is  21  cents 
per  1,000  gallons. 

Pumps. — For  gen- 
eral purposes  some  of 
the  many  types  of 
combination  lift  and 
force  pumps  now  on 
the  market  are  com- 
monly used.  Pumps 
of  this  type  may  be  had  which  are  directl}- 
geared  to  a  gas  or  steam  engine,  or  to  an 


Fig.     120. — Pumping    jack 

for    applying    power    to    a 

hand  pump 


228 


GREENHOUSES 


electric  motor.  Usually,  a  hand  pump  of 
large  size  is  used,  and  power  is  applied  by 
means  of  a  pumping  jack. 

A    very    efficient    but    somewhat    delicate 
pumping    device    is    the    combined    hot-air- 
engine    and    pump. 


These 
very  good  satisfac- 
tion where  the  water 
is  reasonably  close 
to  the  surface,  or 
when  it  does  not 
have  to  be    pumped 


^5 1  I  5  ^  ^ 


Ui^ 


W£IL  CASfAfa 
*—/.Okv  ir/Ar£P  C£y£t. 


COMPRESSED 
AIR 


iAKP£AS£/9 

3/'a"^/P£ 


/V«6 
Oro-  PA/£L/MAt  r/c 


agamst  too  great  a 
pressure.  Improved 
types  of  large  size 
are  now  available, 
and  are  very  econ- 
omical of  fuel,  but 
the  engine  is  not  as 
well  adapted  for 
general  power  pur- 
poses as  are  gas  en- 
gines. 

A  form  of  pump,  which  is  becoming  quite 
popular  for  domestic  use  is  the  auto-pneu- 
matic pump.  It  is  designed  to  be  used  in 
an  open  well  or  a  cased  well  of  large  bore, 
as  the  pump  proper  is  placed  entirely  be- 


Fig.    121. — Diagram    showing 
installation       of       an       auto- 
pneumatic   pump 


IRRIGATION  229 

neatli  the  water.  It  is  operated  by  com- 
pressed air,  hence  an  air  pump  and  an  air 
tank  are  required.  Its  chief  advantage  for 
domestic  purposes  lies  in  the  fact  that  it 
starts  automatically  when  the  faucet  is 
opened,  thus  giving  a  supply  of  cold  water 
direct  fr.om  the  well.  For  greenhouse  pur- 
poses this  is  a  disadvantage,  as  the  water  may 
be  too  cold  to  use  on  the  plants. 

Pump  cylinders  should  not  be  more  than 
20  feet  above  the  surface  of  the  water,  as  this 
is  the  limit  of  practical  suction.  When  the 
water  is  more  than  20  feet  below  the  surface 
the  pumping  cylinders  are  lowered  accord- 
ingly. In  deep  wells  it  is  common  to  lower 
the  pumping  cylinders  well  into  the  water. 

Capacity  of  Pumps. — The  capacity  of  a 
pump  depends  upon  the  size  of  the  cylinder 
and  the  length  and  rapidity  of  the  strokes. 
The  table  on  page  230  gives  the  discharge  per 
stroke  in  gallons,  of  pumps  having  cylinders 
of  various  sizes.  This,  multiplied  by  the 
number  of  strokes  per  minute,  will  give  the 
capacity  per  minute. 

Power  Required. — The  power  required  to 
operate  a  given  pump  may  be  determined  as 
follows:  Multiply  the  number  of  gallons 
pumped  per  minute  tfy  8.357  pounds  (the 


230  GREENHOUSES 


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IRRIGATION  231 

weight  of  a  gallon  of  water).  This  will  give 
the  weight  pumped  per  minute.  Multiply 
this  by  the  total  lift  in  feet.  This  will  give 
the  number  of  foot-pounds  of  energy  required 
per  minute.  Divide  this  by  33,000  (the  num- 
ber of  foot-pounds  in  a  horse-power)  and  the 
result  will  be  the  number,  of  horse-power  re- 
(juired.  Pumping  outfits  are  only  about  50 
per  cent,  efficient,  so  that  the  results  ob- 
tained by  the  above  are  doubled  in  actual 
practice.  On  the  average  one  horse-power 
will  pump  30  gallons  per  minute  to  the  height 
of  100  feet.  In  pumping  water  against  press- 
ure in  a  pneumatic  tank,  extra  power  will 
1)e  required.  Extra  power  will  also  be  re- 
quired when  the  waten  is  pumped  for  any 
considerable  distance,  on  account  of  the  fric- 
tion of  the  pipes.  The  frictional  loss  in  feet 
of  lift  for  each  100  feet  of  pipe  of  various 
sizes  is  shown  in  the  following  table. 


Gallons 

Size 

of   Pipe 

per  min. 

34  m. 

lin. 

114  in. 

VAm. 

2  in. 

2V2  ir 

Frictional  Loss 

10 

29.9 

7.3 

1.4 

1.0 

0.28 

0.09 

IS 

66.0 

16.1 

5.5 

22 

0.57 

0.18 

20 

115.0 

28.0 

9.5 

4.8 

0.96 

0.32 

25 

179.0 

43.7 

14.7 

6'.0 

1.7 

0.48 

30 

264.0 

63.2 

21.0 

8.6 

2.1 

0.69 

35 

372.0 

85.1 

28.9 

11.6 

2.7 

0.92 

40 

461.0 

110.0 

37.0 

14.9 

z:j 

1.2 

232 


GREENHOUSES 


This  loss  by  friction  cannot  be  disregarded. 
Suppose,  for  example,  it  is  desired  to  deliver 
20  gallons  per  minute  at  a  distance  of  100 
feet.  By  referring  to  the  above  table  it  will 
be  seen  that  if  a  ^4-inch  pipe  were  used,  a 
loss  equal  to  a  head  of  115  feet  would  be 
sustained,  while  if  a  i%-inch  pipe  were  used 
a  loss  of  only  4.8  feet  would  be  sustained. 
It  is  economy  to  use  pipe  of  generous  size. 

Hydraulic  Rams. — The  hydraulic  ram  is 
a  device  which  utilizes  the  force  of  water, 


Fig.  122. — A  simple  type  of  hydraulic  ram.     a,  int?^ke 
pipe^    f,    delivery    pipe 


IRRIGATION  233 

falling  a  short  distance,  to  elevate  a  portion 
of  the  water  to  a  greater  height.  It  is 
wasteful  of  water,  but  when  a  never-failing 
stream  of  sufficient  flow  and  fall  is  avail- 
able it  is  one  of  the  most  economical  and 
satisfactory  of  water-lifting  machines. 

Rams  are  somewhat  difficult  to  install  by 
a  novice,  because  of  the  rather  exacting  con- 


%-:r' 

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r»u  ftcr 

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Fig.    123. — Plan    for   installing   a    hydraulic   ram 

ditions  necessary  to  secure  the  most  efficient 
service.  When  they  are  properly  installed, 
however,  they  give  little  trouble,  provided 
they  are  kept  from  freezing. 

Capacity  of  Rams. — To  And  the  capacity 
of  a  ram  for  any  given  conditions  proceed  as 
follows :  Multiply  the  fall  in  feet  by  the  quan- 
tity of  water  which  may  be  supplied  to  the 
ram  in  gallons  per  minute,  and  divide  the 
product  by  the  height  the  water  is  to  be 
raised.  -The  result  will  be  the  number  of 
gallons  delivered  per  minute,       The  above 


234  GREENHOUSES 

disregards  loss  by  friction  and  assumes  that  a 
ram  of  the  proper  size  is  installed. 

By  use  of  the  table  on  page  235  an  estimate 
of  the  capacity  of  a  ram  for  different  con- 
ditions may  be  determined.  The  left-hand 
column  indicates  the  number  of  feet  of  fall 
possible  to  secure,  and  the  numbers  at  the  top 
of  the  vertical  columns  indicate  the  height 
to  which  water  is  to  be  raised. 

For  example:  Suppose  we  have  a  stream 
with  a  flow  of  100  gallons  per  minute;  that 
there  is  an  available  fall  of  10  feet,  and  that 
it  is  desired  to  raise  the  water  40  feet.  The 
factor  in  this  case  (252)  will  be  found  in  the 
column  headed  by  40  and  opposite  the  num- 
ber 10  under  power  head.  Multiplying  252 
by  100,  we  have  25,200,  the  number  of  gal- 
lons that  may  be  delivered  per  day  by  a  ram 
of  the  correct  size. 

In  ordering  a  hydraulic  ram  the  following 
information  should  be  given: 

1.  Flow  of  water  in  gallons  per  minute. 

2.  Vertical  fall  in  feet. 

3.  Distance  in  which  fall  is  obtained. 

4.  Vertical  height  above  ram  the  water 
is  to  be  raised. 

5.  Distance  water  is  to  be  forced. 

6.  Number  of  gallons  required  per  day. 


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To  use:  Multiply  the  factor  opposite  power  head  and  under 
purriping  head  by  the  number  of  gallons  of  water  avail- 
able per  minute.  The  product  will  be  the  number  of 
gallons  delivered  per  day.  (See  page  234.) 


23G  GREENHOUSES    ^ 

Double-acting  rams  which  will  utilize  the 
water  from  a  creek  or  river  as  power  and 
pump  water  from  a  spring  or  shallow  well 
may  be  had,  but  they  are  somewhat  more 
complicated. 

Windmills  for  Pumping. — The  chief  ob- 
jection to  the  windmill  for  pumping  is  its  lack 
of  dependability.  Where  the  wind  is  fairly 
constant,  or  when  a  large  storage  capacity 
may  be  had  cheaply,  windmills  are  the  cheap- 
est source  of  power.  On  the  average  the 
windmills  used  for  pumping  develop  about 
three-fourths  horse-power.  The  geared  steel 
wheel  mills  are  more  efficient  and  will  run 
in  lighter  winds  than  will  the  wood  wheel 
mills. 

Storage  Tanks. — Storage  tanks  are  neces- 
sary with  most  water  systems,  to  insure  a 
constant  supply  and  to  furnish  pressure. 
They  fall  naturally  under  two  heads:  (i) 
Open  tanks  in  which  pressure  is  obtained  by 
gravity;  (2)  closed  tanks,  usually  pneumatic 
tanks,  containing  air  into  which  water  is 
forced,  the  compressed  air  in  this  case  furn- 
ishing the  desired  pressure. 

In  placing  tanks  in  the  attic,  or  other  ele- 
vated positions,  it  is  well  to  keep  in  mind  the 


IRRIGATION  237 

■weight  of  water  and  to  see  that  the  supports 
are  amply  strong.  For  example,  a  lo-barrel 
tank  of  water  will  weigh,  in  addition  to  the 
tank  itself,  more  than  one  and  a  quarter 
tons. 

The  pressure  to  be  obtained  from  elevated 
tanks  depends  upon  their  elevation,  each  ad- 
ditional foot  giving  a  pressure  of  about  0.433 
pounds  per  square  inch.  The  following  table 
shows  the  pressure  (disregarding  friction) 
to  be  obtained  at  various  heights. 

Height  in  feet  Pressure  per  sq.  inch 

10   4.33  pounds 

20  8.66 

30  12.99 

40  17.32 

50  21.65 

60 25.98 

70  30.31 

80  34.64 

90  38.97 

The  advantage  of  the  pneumatic  tank  lies 
in  the  fact  that  it  may  be  placed  in  any  out- 
of-the-way  place  in  the  basement,  or  it  may 
be  buried  in  the  ground  below  the  frost  line. 
There  is  little  danger  in  its  use  if  it  is  pro- 
vided with  a  pressure  gauge  and  safety  valve. 

Capacity  of  Storage  Tanks. — The  capac- 
ity of  storage  tanks  is  not  difficult  to  arrive 
at  by  simple  mathematics,  unless  they  are 


238  GREENHOUSES 

of  unusual  shapes.  For  convenience,  tables 
are  given  below  showing  the  capacity  of 
round  and  square  tanks  of  standard  sizes. 
When  pneumatic  tanks  are  used,  about  a 
third  of  their  capacity  is  occupied  by  the 
compressed  air. 

TABLE  SHOWING  CAPACITY  OF  ROUND 
STORAGE  TANKS 

Diameter  Height  Capacity  Diameter     Heig-ht         Capacity 


Feet 

Feet 

Gallons 

Feet 

Feet 

Gallons 

4 

4 

378 

5 

6 

735 

4 

5 

470 

5^: 

8 

1400 

4 

6 

567 

6 

2 

423 

4 

8 

756 

6 

2Vi 

528 

5 

3 

440 

6 

3 

635 

5 

4 

588 

6 

4 

845 

5 

5 

735 

6 

5 

1066 

TABLE  SHOWING  CAPACITY  OF  RECTANGULAR 
TANKS 

Width  Height  Length         Capacity 

Feet  Feet  Feet  Gallons 


2^ 

2/2 

8 

378 

3 

2 

8 

360 

3 

2 

10 

448 

3 

^; 

8 

448. 

3 

2^: 

10 

565 

3 

3 

10 

673 

4 

2 

8 

478 

4 

2 

10 

598 

4 

2J^: 

8 

598 

4 

2/i 

10 

748 

4 

3 

8 

718 

IRRIGATION 


239 


240 


GREENHOUSES 


IRRIGATION 
There  are  two  general  methods  of  water- 
ing greenhouse  crops  aside  from  hand  water- 
ing.     One  is  by  an  overhead  sprinkling  sys- 
tem ;  the  other  is  by  an  underground  or  sub- 
irrigating  system.       Of  these  the  overhead 
system  is  by  far  the  more  popu- 
lar.   A  census  of  a  large  number 
of  growers  of  greenhouse  vege 
tables  shows  that  practically  75 
per  cent,  use  some  form  of  over- 
head irrigation,  while  only  two 
out  of  the  whole    number    con- 
sulted were  using  sub-irrigation. 
Practically  the  only  system  of 
overhead      irrigation     used     in 
greenhouses    is    one    in    which 
pipes,  fitted  with  nozzles  which 
Fig.    125  —  A  throw  a  rain-like  spray,  are  run 

type  of  nozzle  .  ,.        •  r    .  i        i  i 

used  in  over-  Icngthwisc  01  the  housc  and  so 
head  irrigation  arranged  that  they  may  be  rotat- 
ed to  throw  the  spray  on  both  sides  of  the  pipe 
line.  The  original  system  is  known  as  the 
Skinner  system,  but  there  are  others  now 
on  the  market.  Pipe  lines  for  this  system 
should  be  about  i6  feet  apart  and  as  far  from 
the  foliage  as  possible.  The  nozzles  should 
be  3  feet  apart.      This  system  will  operate 


IRRIGATION 


241 


satisfactorily  on  a*  water   pressure  of  from 
lO  to  30  pounds. 

When  constructing  benches  for  sub-irriga- 


Fig.  126. — Greenhouse  bench  arranged  for  sub-irrigation. 
A,  cement  troughs  on  bottom  of  bench;  B,  drain  tile  or 
perforated  pipes  for  supplying  water;  C,  drainage  spaces 
between   troughs. 

tion,  the  essentials  are  a  water-tight  bottom, 
usually  of  cement,  to  prevent  the  water  from 
leaking  through,  and  perforated  pipes  or  tiles 
for  distributing  it  along  the  bench.  This 
system  has  been  tried  out  extensively  with 
varying  results  by  the  Ohio  experiment 
station. 


CHAPTER  XV 
CONCRETE  CONSTRUCTION 

Concrete  is  a  combination  of  Portland 
cement,  sand,  crushed  stone  or  gravel  and 
water,  thoroughly  mixed  and  then  allowed 
to  set  or  harden. 

Portland  cement,  or  cement,  as  it  is  now 
commonly  known,  is  manufactured  by  burn- 
ing and  grinding  together-  limestone  and 
clay,  or  shale,  in  certain  proportions.  It  de- 
rives its  name,  Portland  cement,  from  its  re- 
semblance to  Portland  stone.  It  is  also 
sometimes  known  as  hydraulic  cement,  or 
building  cement. 

Concrete  has  wellnigh  revolutionized 
building  practice  in  the  last  25  years,  but  in 
no  case  has  it  displaced  masonry  to  a  greater 
extent  than  in  greenhouse  construction. 
Formerly,  the  walls  of  a  greenhouse  were  a 
source  of  much  trouble,  because  of  their 
rapid  deterioration,  but  it  was  soon  found 
that    when    conc'rete    was    used    they    be- 

242 


CONCRETE  CONSTRUCTION  243 

'  came  the  most  stable  part  of  the  structure. 
Concrete  is  practically  the  only  material  now 
used  for  the  foundations  and  walls  of  com- 
mercial greenhouses,  and  to  a  great  extent 
it  has  displaced  masonry  for  private 
greenhouses. 

At  present  cement  is  almost  universally 
handled  and  shipped  in  cloth  or  paper  sacks 
holding  95  pounds.  It  is  often  spoken  of, 
and  is  sometimes  quoted  by  the  barrel,  'this 
now  meaning  simply  four  sacks,  or  380 
pounds.  As  a  rule,  the  most  satisfactory 
form  in  which  to  buv  cement  is  in  cloth  sacks. 
The  sacks  may  be  returned  when  empty,  and 
if  not  torn  a  credit  of  about  10  cents  each 
may.be  realized. 

Sand. — Sand,  to  give,  the  most  satisfac- 
tory results,  should  be  free  from  clay  or  or- 
ganic matter,  and  rather  coarse.  Very  fine 
sand  will  require  a  greater  proportion  of 
cement  and  as.  a  consequence  the  concrete 
will  be  more  expensive.  In  a  small  way, 
sand  that  contains  some  organic  material 
may  be  washed  and  thus  made  satisfactory, 
but  it  is  an  expensive  process. 


244  GREENHOUSES 

Stone. — Either  crushed  stone  or  gravel 
may  be  used  in  making  concrete,  the  only 
difference  being  that  the  crushed  stone  usual- 
ly has  a  cleaner  surface  and  the  cement  will 
cling  to  it  more  tightly.  When  gravel  is 
used  it  should  be  free  from  clay,  and  the  in- 
dividual stones  should  be  clean  and  bright 
and  not  covered  with  a  layer  o£  clay  or  soil. 

The  size  of  the  stones  may  range  from  a 
fourth  to  two  and  a  half  inches  in  diameter, 
the  size  depending  on  the  use  to  which  the 
concrete  is  put.  The  best  results  are  ob- 
tained when  the  sizes  vary  regularly  from 
small  to  large,  in  order  that  they  may  settle 
well  together  when  the  concrete  is  poured. 

Run  of  the  Bank  gravel  is  sometimes  used. 
This  is  economical  only  when  it  contains 
sand  and  gravel  in  the  correct  proportions, 
as  explained  in  a  succeeding  paragraph. 

Crushed  Stone  may  also  contain  very  fine, 
medium  and  coarse  stone  in  the  correct  pro- 
portions, so  that  no  sand  need  be  added,  but 
such  a  condition  is  rare,  unless  tlie  stone  is 
ground  and  furnished  for  this  special  pur- 
pose. 


CONCRETE  CONSTRUCTION 


24.5 


'  Proportions  of  Materials. — Theoretically, 
the  ideal  concrete  is  a  mixture  in  which  all 
the  spaces  between  the  stones  or  gravel  are 


^^A/O 


Sto/v£: 


COA/C/?£T£ 


Fig.    127. — Proportions    of    cement,    sand    and    stone   re- 
quired to  form  concrete 

filled  with  sand,  and  all  the  spaces  between 
the  grains  of  sand  are  filled  with  cement. 
From  this  it  will  be  seen  that  the  total  bulk 
of  concrete  would  not  be  greatly  in  excess 
of  the  bulk  of  stone  or  gravel,  as  the  sand  and 
cement  would  go  to  fill  the  vacant  spaces 
(voids).  This  is  really  true  except  that,  as 
usually  proportioned,  a  slight  excess  of  ce- 
ment is  allowed.  This  is  wise  in  order  to 
insure  that  thene  shall  be  a  film  of  cement 
about  each  stone  and  grain  of  sand,  so  they 
may  be  all  bound  together  in  a  solid  mass. 
The  common  formula  for  most  concrete 
work  is  known  as  the  i  :2  4  mixture.  In  this 
there  are:  i  part  by  measure  of  cement,  2 
parts  of  sand,  and  4  parts  of  stone  or  gravel. 


246  GREENHOUSES 

This  is  the  formula  commonly  used  for  walls 
above  ground  and  for  bridges  and  similar 
work.  For  sidewalks,  floors,  etc.,  which  are 
supported  on  a  Arm  foundation  and  are  not 
subjected  to  heavy  strain,  a  weaker  mixture 
of  I  part  of  cement,  2M  parts  of  sand  and  5 
parts  of  stone  or  gravel,  is  sometimes  used. 
For  plastering  the  outside  of  walls  and  for 
similar  purposes  a  mixture  of  cement  and 
sand  alone  in  the  proportion  of  i  to  i  is  used, 
as  it  is  easily  worked  and  leaves  a  smooth 
surface. 

Mixing. — For  small  jobs  concrete  is 
usually  mixed  by  hand.  The  essentials  are: 
( I )  A  tight  platform  or  mixing  board  of  suf- 
ficient size;  (2)  a  convenient  measuring  box; 
(3)  suitable  shovels;  and  (4)  a  supply  of 
water.  Quite  commonly  the  sand  and  gravel 
is  measured  in  the  wheelbarrows  in  which 
it  is  hauled,  a  little  experience,  secured  by 
carefully  measuring  the  amount  for  a  few 
times,  being  all  that  is  necessary  to  insure 
sufficiently  accurate  measuring.  The  bar- 
row loads  are  checked  up  from  time  to  time, 
however,  to  see  that  they  are  not  over-run- 
ning or  falling  short. 


CONCRETE  CONSTRUCTION  247 

It  is  convenient  to  mix  in  batches  requir- 
ing even  bags  of  cement.  For  example,  a 
two  bag  batch  would  mean  two  bags  of  ce- 
ment, a  quantity  of  sand  equal  to  4  bags 
(3K  cubic  feet)  and  8  bags  (7M  cubic  feet) 
of  stone  or  gravel.  They  are  mixed  together 
thoroughly,  shoveling  over  several  times  be- 
fore  adding  the   water. 

Amount  of  Water. — The  quantity  of  water 
used  has  but  little  effect  on  the  resulting  con- 
crete, the  amount  depending  rather  on  the 
consistency  at  which  the  concrete  can  best 
be  handled  for  the  special  purpose  for  which 
it  is  to  be  used.  The  dryer  the  mixture  the 
more  quickly  it  will  set. 

For  thin  walls,  or  where  the  form  con- 
tains many  indentations,  the  mixture  should 
be  thin  enough  to  run  off  the  shovel  quickly 
in  handling. 

For.  walls  of  medium  thickness  (6  to  12 
inches)  or  for  floors,  walks,  etc.,  it  should  be 
jelly-like  in  consistency,  so  that  it  will  pile 
up  somewhat  on  the  shovel,  but  will  slowly 
settle  and  run  off  the  sides. 

For  foundations,  underground,  where  it  is 
important  that  the  mixture  set  as  quickly  as 


248  GREENHOUSES 

possible,  it  may  be  mixed  so  dry  that  it  will 
handle  like  damp  earth.  Care  must  be  taken 
in  making-  this  ''dry  mixture"  that  every  part 
is  moistened. 

Estimating  Materials. — The  quantity  of 
cement,  sand  and  gravel  necessary  for  a  giv- 
en piece  of  work  may  be  found  by  multiply- 
ing the  number  of  cubic  feet  by  the  percent- 
age of  cement,  sand  and  gravel  in  a  cubic 
foot  of  the  mixture  to  be  used.  For  con- 
venience these  proportions  are  given  in  tabu- 
lar form  in  terms  of  barrels  of  cement  and 
cubic  yards  of  sand  and  gravel. 

TABLE     SHOWING     PROPORTIONATE    QUANTI- 
TIES OF  CEMENT,  SAND  AND  GRAVEL  IN 
A  CUBIC  FOOT  OF  CONCRETE 

Cement                Sand  Stone  or  gravel 

Mixture              barrel  cubic  yard  cubic  yard 

1:2     :4              0.058                   0.0163  0.0326 

1:2J^:5             0.048                  0.0176  0.0352 

To  use,  multiply  the  number  of  cubic  feet 
of  concrete  required  by  the  factor  shown  in 
the  table.  The  result  will  be  the  quantity  of 
the  material  required. 

For  example,  looo  cubic  feet  of  i  '.2:4.  con- 
crete would  require 


CONCRETE  CONSTRUCTION  249 

1000  X  0.058  or  58  barrels  of  cement 
1000  X  0.163  or  16.3  cubic  yards  sand 
1000  X  0.0326  or  32.6  cubic  yards  gravel 
In  estimating  for  cement  mortar,  figure  i 
cubic  foot  to  each  15  square  feet  of  surface  to 
be  covered.     Each  cubic  foot  of  i  :i  sand  and 
cement  mortar  requires  0.1856  barrels  of  ce- 
ment and  0.0263  cubic  yards  of  sand. 

Forms. — As  concrete  is  soft  when  mixed, 
it  is  necessary  to  have  some  kind  of  a  form 
or  mold  to  hold  it  in  the  desired  form  and 
position  until  it  hardens.  For  foundations, 
for  such  structures  as  greenhouses,  a  trench 
is  usually  dug  12  or  14  inches  wide,  and  deep 
enough  so  that  the  bottom  will  be  below 
the  frost  line.  If  the  soil  is  firm  enough  to 
hold  its  place  no  form  will  be  needed,  but 
the  concrete  may  be  poured  directly  into  the 
excavation,  tamped  and  allowed  to  harden. 

For  that  part  of  the  wall  which  is  above 
ground,  however,  a  form  is  needed.  It  is 
important  that  this  form  be  vertical,  that 
it  be  straight,  and  that  it  be  smooth  in  tlie 
inside  so  that  the  resulting  waH  will  be  agree- 
able to  the  eye.  •  The  making  of  the  forms  is 
important.  They  should  be  built  by  an  ex- 
perienced carpenter. 


250 


GREENHOUSES 


Any  kind  of  lumber  which  is  free  from 
knot  holes  and  has  been  surfaced  to  an  even 
thickness  will  answer  for  forms.  If  the  wall 
is  a  high  one  it  may  be  necessary  to  tie  the 
sides  of  the  form  together  with  wire.  The 
wires  remain  in  the  concrete  when  the  form 
is  removed,  but  may  be  cut  off  flush  with  the 
surface,  and  if  the  wall  is  plastered  they  will 
not  be  noticed. 


Fig.  128. — Form  for  a  concrete  wall 


CONCRETE  CONSTRUCTION 


251 


Filling  the  Forms. — In  filling  the  form  the 
concrete  is  placed  in  layers  about  6  inches 
deep  and  tamped  lightly  until  water  shows 
on  the  surface.  This  will 
insure  its  settling  together 
closely-  If  the  wall  is  not 
to  be  plastered  and  a  smooth 
surface  is  required,  a  spade 
or  paddle  is  run  down  all 
along  between  the  concrete 
and  the  sides  of  the  form 
when  the  concrete  is  poured. 
This  will  force  the  larger 
stones  toward  the  center  of 
the  wall  and  allow  the 
smaller  stones  and  sand  to 
fill  in  next  to  the  form,  thus 


Fig.  129.— Meth- 
od   of    facing    a 
concrete  wall 


making  a  smooth  surface. 


Reinforcing.  —  Concrete 
will  withstand  enormous 
crushing  loads,  but  in  walls  where  there 
is  a  considerable  side  strain,  it  should  be 
reinforced  with  iron  or  steel.  The  best 
materials  for  this  purpose  are  iron  or  steel 
rods.  If  they  are  twisted  or  roughened  in 
some  manner,  so  that  the  concrete  will  ad- 
here to  them  tightly,  their  efiiciency  will  be 
greatly   increased.       They  are   put   in    the 


252  GREENHOUSES 

forms,  usually  vertically,  about  midway  be- 
tween the  sides  and  2  or  3  feet  apart  before 
the  concrete  is  poured. 

When  an  extra  strong  wall  is  required  rods 
may  be  laid  horizontally  on  the  top  of  every 
layer  or  every  second  layer  as  the  concrete  is 
placed  and  tamped  down  into  the  soft  mix- 
ture. When  the  walls  extend  onl}^  3  or  4  feet 
above  the  surface  and  are  at  least  8  inches 
thick  as  is  commonly  the  case  in  greenhouses, 
little  if  any  reinforcement  is  needdd. 

Walks  and  Floors. — Concrete  walks  are 
now  very  commonly  used  in  commercial  as 
well  as  private  greenhouses,  and  the  boiler 
and  service  rooms  are  usually  floored  with 
concrete.  As  the  walks  are  not  usually  sub- 
ject to  as  hard  usage  as  those  laid  out-of- 
doors,  or  to  the  action  of  frosts,  it  is  not 
necessary  to  make  them  quite  as  thick,  but  in 
other  respects  they  differ  but  little  from  the 
concrete  sidewalks  now  so  common. 

The  common  method  of  building  walks  in 
a  greenhouse  is  to  make  an  excavation  a  few 
inches  deep  and  as  wide  as  the  walk  is  to  be 
and  fill  it  with  broken  stone,  pieces  of  brick, 
etc.,  to  make  a  foundation.  On  top  of  this, 
two  pieces  of  straight  2  x  4-inch  lumber  are 
placed  on  edge,  level  with  each  other  and 


CO^XRETE  COXSTRUCTION  253 

with  their  inside  edges  spaced  just  as  far 
apart  as  the  walk  is  to  he  wide.  They  are 
then  fastened  by  driving  stakes  on  the  out 
side  and  naihng.  The  concrete  is  then 
poured  into  this  form  to  within  about  an  inch 
of  the  top  and  tamped  firmly.  A  top  coat, 
usually  of  finer  material,  is  then  placed  on 
top  of  the  first  layer  before  it  is  set,  and 
struck  off  by  running  a  straight  edge  along 


Fig.  130. — Structure  of  a  concrete  walk,     a,  foundation; 
"b,  coarse  concrete;  c,  finish  coat  of  fine  concrete 

the  tops  of  the  side  pieces.  This  is  then 
troweled  by  hand  to  give  a  smooth  and 
slightly  curving  surface. 

To  allow  for  expansion  and  contraction, 
the  walk  should  be  cut  into  blocks  before  it 
sets.  This  may  be  done  by  putting  in  pieces 
of  thin  sheet-iron  at  regular  intervals  to  be 
removed  when  the '  concrete  has  partially 
hardened.  Sometimes  the  walk  is  cut 
through  with  a  spade  while  still  soft,  at  regu- 
lar intervals  and  fine,  dry  sand  placed  be- 
tween the  blocks  so  made.  Tliis  is  usually 
quite  satisfactor3^  and  by  careful  troweling 


254  GREENHOUSES 

a  very  neat  walk  may  be  made  in  this  way. 

For  the  lower  layer,  when  there  is  a  firm 
foundation,  a  i  :2>^  15  mixture  will  be  satis- 
factory. The  top  layer  should  be  of  a  1:2 14 
mixture  or,  when  an  especially  smooth  sur- 
face is  required,  of  a  1:2  mixture,  that  is, 
one  part  of  cement  and  two  parts  of  sand. 

Floors  are  laid  ^practically  the  same  as 
walks,  except  that  they  are  usually  troweled 
level  instead  of  curving.  The  work  is  begun 
at  one  side  of  the  floor,  and  as  soon  as  one 
section  has  been  laid  and  has  had  time  to 
set,  the  side  boards  are  taken  up  and  put 
down  for  the  next  section.  Floors  should 
seldom  or  never  be  laid  in  a  solid  mass. 

Waterproofing. — Much  trouble  is  often 
experienced  in  underground  boiler  rooms 
from  water.  The  best  protection  is  to  lay 
a  row  of  tile  completely  around  the 
outside  of  the  foundation,  at  the  bottom,  and 
connect  it  with  the  sewer  or  drain.  If  the 
bottom  of  the  cellar  is  springy  it  may  be 
necessary  to  lay  the  floor  in  a  solid  piece  and 
in  two  layers.  After  the  first  layer  has  set 
and  become  dry,  or  nearly  so,  a  thick  coating 
of  hot  tar  may  be  applied,  allowing  it  to  ex- 
tend for  a  few  inches  up  the  side  walls. 
When  this  has  hardened  put  on  another  coat 


CONCRETE  CONSTRUCTION 


355 


of  rich  concrete,  troweling  it  up  the  sides 
as  far  as  the  tar  has  been  placed.  When  an 
absolutely  watertight  job  is  required  it  may 
be  necessary  to  coat  the  entire  outside  sur- 
face of  the  walls  with  tar  and  then  bank  up 
with  earth. 

Several  so-called  waterproofing  materials 
designed  to  be  placed  in  the  concrete  when 


131. — A   small  power  machine  for  mixing  concrete 


it  is  mixed  are  on  the  market,  but  as  a  rule 
they  are  not  fully  satisfactory. 

Concrete  Blocks. — Blocks  made  of  con- 
crete in  special  molds  or  forms  are  sometimes 
employed  for  walls.  They  are  usually  hol- 
low and  for  that  reason  make  a  warmer  and 
somewhat  dryer  wall  than  does  solid,  poured 


256  GREENHOUSES 

concrete.  Experience  shows  that  as  a  rule 
they  are  less  durable  than  solid  walls,  but 
when  the  cost  of  material  and  labor  for  mak- 
ing forms  is  considered  they  may  be  more 
economical.  They  are  often  made  with  an 
ornamental  face  resembling  broken  stone, 
and  make  a  somewhat  more  pleasing  appear- 
ance than  a  plain  wall. 

Cost  of  Concrete. — So  many  factors  enter 
into  the  cost  of  concrete  that  no  reliable 
general  estimate  can  be  given.  The  price  of 
cement  is  now  fairly  constant  and  uniform. 
The  cost  of  sand  and  gravel  or  crushed  stone, 
on  the  other  hand,  differs  widely.  In  some 
places  it  may  be  had  on  the  premises,  in 
others  it  may  have  to  be  transported  for 
several  miles.  Other  factors  entering  into 
the  cost  are  labor  and  the  size  of  the  opera- 
tion. Where  the  quantity  of  work  will  justi- 
fy the  use  of  a  power  mixing  machine,  the 
cost  is  usually  less  than  when  the  mixing  is 
done  by  expensive  hand  labor,  although  the 
cost  for  labor  may  often  be  greatly  reduced 
by  carefully  planning  the  work. 

In  general  the  contract  prices  for  walls  on 
comparatively  small  jobs  range  from  7  to  20 
cents  per  cubic  foot,  and  for  walks  and  floors 
from  4  to  15  cents  per  square  foot. 


CHAPTER  XVI 
PLANS  AND  ESTIMATES 

The  cost  of  any  kind  of  a  building  must 
necessarily  vary  with  the  cost  of  building 
material  and  the  price  of  labor.  This  is  es- 
pecially true  with  greenhouses,  since  the  ma- 
terials used  (glass  especially)  are  subject 
to  extreme  fluctuations  in  price.  In  the  pre- 
ceding chapters  it  has  been  the  aim  to  give 
all  the  data  necessary  for  estimating  the 
amount  of  material  required  for  any  given 
house,  but  no  attempt  has  been  made  to  state 
definite  prices. 

Little  can  be  added  in  this  chapter  to  what 
has  already  been  given,  and  it  would  be  use- 
less repetition  to  collect  the  data  into  one 
chapter,  as  it  may  be  easily  found  by  refer- 
ring to  the  index.  An  effort  has  been  made, 
however,  to  make  some  suggestions  as  to  the 
probable  cost  of  different  types  of  houses  un- 
der varying  conditions. 

Basis  of  Estimates. — Since  the  economic 
value  of  a  greenhouse  depends  on  the  area  of 

257 


258  GREENHOUSES 

surface  covered  (bench  space)  it  is  common 
to  estimate  costs  in  terms  of  square  feet  of 
surface  covered.  In  an  investigation  among 
a  large  number  of  growers  (all  types  of 
houses)  the  author  found  that  the  first  cost 
averaged  not  far  from  45  cents  per  square 
foot  of  surface  under  glass.  This  included 
cost  of  heating  system,  but  did  not  include 
cost  of  service  buildings. 

The  cheapest  plant  on  which  data  was  se- 
cured was  a  range  of  four  all  wood  frame 
houses,  16  X  50  feet,  which  had  been  in  serv- 
ice for  nine  years  and  which  was  built  at  a 
cost  of  $525,  or  about  22  cents  per  square 
foot.  In  this  case  a  second-hand  boiler  was 
used.  Several  larger  ranges  heated  by  steam 
from  a  central  heating  plant  have  been  built 
at  a  cost  of  between  30  and  40  cents  per 
square  foot,  though  at  a  time  when  material 
was  low  in  price.  Data  on  modern  semi- 
iron  construction,  when  the  labor  was  per- 
formed for  the  most  part  by  the  owner  and 
his  help,  show  a  cost  of  between  50  and  60 
cents  per  square  foot,  and  all  iron  construc- 
tion between  60  and  75  cents  per  square  foot. 
All  these,  of  course,  were  standard  commer- 
cial houses.       Private  and  public  conserva- 


PLANS  AND  ESTIMATES  259 

tories  and  ornamental  houses  often  cost  two 
and  three  times  as  much. 

Detailed  Estimates. — Detailed  estimates 
necessarily  differ  with  the  grade  of  material 
used.  The  following  is  a  detailed  estimate 
at  current  prices  of  the  material  needed  for 
and  the  cost  of  a  sem-iron  frame  house 
30  X  90  feet,  not  including  labor  of  erecting. 

850  cubic  feet  concrete  ('wall  and  piers) — 
50  barrels  cement 
14  cubic  yards  sand 
28  cubic  yards  gravel  $100 

PIPE 

Side  Posts — 

32  pieces  2-inch  pipe,  5  feet  6  inches 
Purlins — 

360  feet  1^  inch 
Purlin  Supports — 

24  pieces  1^-inch  pipe,  8  feet  3  inches 

24  pieces  l>4-inch  pipe,  11   feet 
Cross  Ties — 

24  pieces  1^-inch  pipe,  5  feet 

24  pieces  rj4-inch  pipe,  8  feet  6  inches 
Pipe  and  fittings  for  water  lines,  100  feet  ^  inch'es         $75 

PIPE  FITTINGS 

32  Gutter  brackets 
120  Clamp  fittings 

48  Foot  pieces 
140  Purlin  clasps  $30 

MILL  WORK 

240  feet  sill 

180  feet  eave  plate 


260  GREENHOUSES 

90  feet  ridge 
180  feet  drip  gutter 

4  pieces  gable  rafter,  18  feet  long 
268  pieces  sash  bars,  18  feet  long 

4  pieces   corner  bars,  4  feet  long 
268  pieces  glazing  bars,  4  feet  long 
180  feet  sash  header 
330  feet  glazing  bar 
100  feet  2x4  for  door  casing  and  gable  bracing 

1  door 
Ventilator  sash  with  stops  $200 

GLAZING 
86  boxes  glass  (16x24) 
500  pounds  putty 

8000  glazing  points                     '  $250 

Ventilating  apparatus  $25 

Nails  and  other  hardware  $25 

Paint  $50 

Freight  $15 

Miscellaneous  items  $25 

HEATING 
Boiler  (hot  water) 
Pipe  and  fittings 
Brick  for  flue  $550 


Total $1345 

This  house  covers  approximately  2700 
square  feet  of  surface,  which  at  a  cost  of 
$1,345  gives  a  cost  per  square  foot  of  49.81 
cents  for  materials,  but  not  including  labor. 

Figures  on  a  similar  house  31  x  100  feet 
submitted  by  a  well-known  manufacturer  of 
greenhouse  materials  are  given  below: 


PLANS  AND  ESTIMATES  261 

WOODWORK 
200  feet  gutter  with  drip 
100  feet  ridge 
228  feet  glass  sill 
175  feet  gable  end  bars 

4  pieces  gable  rafters,  18  feet  long 
144  pieces  sash  bars,   18  feet  long 

12  ventilators 

12  pieces  ventilator  sash  cap 

60  headers 
144  side  bars 

4  corner  bars 


1  door 

$177.01 

Ventilating  machine  complete 

$26.40 

Hinges  for  ventilators 

3.60 

Trussing  material 

5.20 

Hardware  for  doors 

.63 

PIPE,  POSTS  AND  FITTINGS  (walls) 

40  pieces  2-inch,  5  feet  long 

40  pieces  post  tops                                       • 

$27.20 

Nails 

2.50 

10  pounds  glazing  paints 

1.30 

400  pounds  putty 

14.00 

Paint 

32.00 

Glass,  4600  square  feet 

260.00 

Purlins,   fittings  and  purlin   supports 

61.75 

Gable  bracing  material 

2.50 

Heating  plant  complete 

70Z.ZZ 

Total 

$1317.42 

The  latter  estimate  does  not  include  cost 
of  materials  for  walls,  but  in  other  ways  is 
complete.  The  cost  per  square  foot  of  sur- 
face covered  is  43.9  cents  not  including  wall 
and  cost  of  erection, 


262  GREENHOUSES 

For  an  all  wood  frame  house  the  cost  of 
material  will  probably  be  from  15  to  25 
per  cent,  less  than  the  above  and»the  cost  of 
erection  from  10  to  20  per  cent.  less. 

For  an  all  metal  frame  house  the  cost  for 
materials  will  range  from  25  to  40  per  cent, 
greater  than  for  the  semi-iron  construction, 
but  the  cost  of  erection  will  be  less. 

Information  Required  for  Estimates. — In 

writing  for  estimates  the  following  informa- 
tion should  be  given : 

1.  Type  of  house  (semi-iron,  all  metal, 
etc.). 

2.  Kind  of  roof  (even  span,  three  quarter 
span,  etc.). 

3.  Length  and  width  (if  range,  send 
sketch  showing  arrangement). 

4.  Height  to  eaves. 

5.  Pitch  of  roof  or  height  to  ridge. 

6.  Size  of  glass  preferred. 

7.  Kind  of  heat  (hot  water,  steam,  vapor). 

8.  Temperature  to  be  maintained. 

9.  Coldest  outside  temperature  expected. 

10.  Kind  of  fuel  (hard  or  soft  coal). 


^ 


INDEX 


A 
All-metal    frame    greenhouses        .  ._ 

Asbestos   covering  for  furnaces  and   pipes 


B 


Beds    (greenhouse) 

curbs  for 

of  hollow  building  tile 
Benches 

arrangement  of 

concrete 

for  sub-irrigation 

height  and  width 

iron  frame 

wood 
Boilers 

accessories   for 

arrangement   for   steam 

cast    iron 

essentials  of 

hot   water 

for  hard   and   soft   coal 

ratings   of 

self   stoking 

steam 

styles   of   cast   iron 

styles   of  wrought  iron 

types   of    . 

under-fed 

wrought    iron 


Cast   iron   boilers    . 
Chimneys    and    flues 

size  and  height  of 
Coal 

cost  of 

heating  value  of 

kinds  of  . 


heati 


"g- 


PAGE 
91 

218 

143 
156 
145 
143 
153 
149 
241 
152 
148 
146 
200 
215 
197 
205 
201 
210 
211 
212 
221 
210 
208 
209 
203 
221 
205 

208 
223 
225 

221 
220 
219 


263 


264 


INDEX 


Coils    (heating)       .... 

arrangement   of        .  .  . 

length  of  for  hot  water  heating 

length  of  for  steam  heating 
Coldframes 

described 

construction  of 
Cold-pits  .... 

Concentric  system  of  framing 
Concrete   construction 

blocks 

cost  of 

estimating    materials 

filling  forms     . 

forms    for 

mixing 

water  needed  for 

water   proofing 
Conservatories 
Curbs 

Curved    eave    construction 
Curved  roof  greenhouse 
Cypress   (pecky)      . 


PAGE 

164 

191 

179 

190 

24 

3 

24 

3,26 

78 

242 

255 

256 

248 

251 

249 

246 

247 

254 

3 

156 

60 

59 

n 


Double  glass  sash 
Drip  gutter     . 


15 
1Z 


Eave   plate 

Even  span  greenhouse   . 

Expansion    tank 


Fire  surface  of  boilers   . 
Flow  pipe,  how  to  find  s 
Flues       .... 

size  and  height  of   . 
Forcing    boxes 
Forcing   houses 
Foundations 
Framework 

classes  of 

erecting 
Framing 
Fuels       .... 


F 
ize  of 


66 

51 

181,187 

202 
175 
223 
225 

29 
3,6 

83 

80 

79,92 

73,  85.  89 

218 


Gable  raftei    . 


73 


INDEX 


265 


Gable   roof   sash-bed 
Gearing,    ventilator 
Glass 

grades  of  . 

quantity  in  box 

sizes  of 

substitutes    for 
Glazing 

butted    method 

lapped    method 

window  and  greenhouse 
Glazing  bars  . 
Glazing  points 
Glazing  ladders 
Glazing  sill 
Grate    surface 
Greenhouses 

architecture   of 

arrangement    of 

circular     . 

curved  eave 

curved    roof 

erection   of 

even  span 

evolution  of 

framing     . 

glass    for 

heating 

lean-to 

location    of 

plans  and  estimates  for 

ridge-and-furrow 

side  hill     . 

size   of 

structural  material  for 

ventilation  of 

uneven   span 
Gutter     . 


Hanging   rail,    sash 
Heat,   loss  by  reflectic.i 
Heating,    greenhouse 

by  hot  water     . 

by  steam 

coils  .       .•  •  • 

combination  systems 


PAGE 

30 
131 

98 

99 
100 
113 

97 
102 
101 
105 

68 
109 
120 

65 
201 

50 
36 
62 
62 
59 
94 
51 

5-9 
78,  85,  89 
97 

158 
50 
35 

259 
56 
60 
40 
63 

121 
54 
66 


76 
42 

158 
167 

188 
164,  179,  191 


163 


266 


INDEX 


principles  of     . 

hot  water  vs.  steam 

with  cast  iron  pipes 

with   flues 
High  pressure  steam  heating 
Hotbed 

construction  of 

described 

heating   by    flues 

location  for 

manure    for 

permanent,  plans  for 

sash  for   . 

temporary,    plans    for 
Hot  water  heating 

advantages    of 

arrangement  of  pipes  for 

estimating  radiation  for 

general    principles    of 

pipe  for   .  .  .  . 

pressure  systems 


PAGE 

158 
159 
164 
159 
196 

10 

2 

23 

11 

21 

19 

11 

20 

159 

159 

169, 178 

171,176 

167 

173 

183 


Irrigation 
overhead 
sub-irrigation 


240 
240 
241 


Light 

loss  by  absorption 

loss  by"  reflection 
Location 

for  greenhouses 

for   hotbeds 


Mats,   sash-bed 
Manure  for  hotbeds 


M 


97 

44 

35 
11 


31 
21 


Paint 

estimating 
for  iron  work 
for   shading 
kinds  of    . 

Painting 

"Pecky"  cypress 


117 
116 
118 
116 
114 

n 


INDEX 


267 


PAGE 


Pipe 

covering  for 

frame 

paint   for 

steel 

wrought   iron 
Pit  for  hotbed 
Pitch  of  roof  . 
Plans  and  estimates 

basis    of  .  .  ... 

detailed  estimates  for  greenhouses 

information   required   for 
Plant   forcers  .... 

Pressure  systems  of  hot  water  heatinr 
Propagating  house 
Pumps 

capacity  of        ...  . 

for  circulating  hot  water 

kinds  of    . 

power  required  for  . 

steam 
Purlins 
Putty 

estimating 

liquid 
Putty  bulb     . 


Radiation,  how  to  estimate 
Rafters    . 
Rams,  hydraulic 

capacity  of 

double  acting   . 

plan  for  installing 
Range  of  glass,  a   . 
Ridge       .         .         . 
Ridge-and-furrow    houses 
Roof,  pitch  of 


Sash 

cost  of 
glazing  of 
kinds  of   . 
temporary 

Sash-bars 

spacing  of 


268 


INDEX 


Sash-beds 

attached    to    dwelling 

classes    of  .  .  .  , 

gable  roof         .  .  .  . 

materials,  care  of     . 
Sash    sill  .  .  .  .  . 

Semi-iron   frame   houses 
Shading        ^  .  .         .-    .      - 

Shaft   hangers  .  .  .,         . 

Shafting,  'ventilator 
Shed  roof  greenhouse     . 
Shutters   ...... 

Side    hill   greenhouse 
Side   ventilating   machinery    . 
Sliding   shaft   ventilating  machine 
Steam  heating  .  .  .  . 

advantages    of  .  .  . 

arrangement  of  boilers   for 

arrangement  of  coils  for 

coils    for  .  .  ..         . 

general  principles     . 

high    pressure 

vacuum  and  vapor  systems 
Steam  pumps  and  traps 
Stove  house    .  .  .  .  . 

Structural   material 
Substitutes   for  glass 


Tanks 

capacity    of 

expansion 

height  of 

types  of   . 
Traps,    steam   return 
Truss    framework 


•    r 

:          28 

2 

'.             30 

33 

65 

' 

88 

118 

130 

128 

50 

33 

60 

126,  K'4 

140 

188 

160 

197 

191 

190 

188 

196 

196 

198 

4 

63 

113 

238 

181,  187 

237 

236 

19S 

91 

u 


Uneven  span  greenhouses 


34 


acuum   systems   of  heating 

196 

apor  systems  of  heating      . 

.         .           196 

entilation      .... 

.   121-141 

overhead            .... 

...           124 

side 

123 

systems  of         ...          . 

124 

under-bench      .... 

125 

INDEX 


260 


Ventilators 

arms    for            ...... 

.    136.138 

header      .          .         :• 

1^ 

methods  of  hanging          .... 

126 

size    of      .          .          .          .          o          .          . 

126 

Ventilating  machinery 

capacity  of        .....          . 

139 

chain    system    ...... 

133 

closed    column           ..... 

132 

gearing 

131 

open   column    ...... 

131 

rack  and  pinion          ..... 

133 

shafting    ....... 

128 

side 

.   134.  136 

sliding  shaft 

140 

W 

Walks 

ashes  used  for           ..... 

156 

concrete    ....... 

252 

construction   of                     .... 

252 

materials  for 

156 

width  of  . 

155 

Walls 

.     83, 251 

Water  supply 

amount  used  in  greenhouses 

226 

cost   of      ......          • 

227 

hj^draulic   rams   for   raising 

232 

pumps  for 

.   227-228 

storage   tanks  for      ..... 

236 

Waterproofing  for  concrete 

254 

Weather  strip          ...... 

16 

Wood,  kinds  used  in  greenhouse   construction 

77 

Wood    frame    greenhouses      .... 

85 

Wrought  iron  boilers 

205 

Wrought  iron  pipe 

89 

;#^' 


rw 


N.  MANCHES1  ER, 


IKiniAM/ 


